Model Applications - Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. However, with stiff springs and heavy weights, the clutch will have to drop well below its engagement RPM before the clutch will once again release. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds.
Stall speed.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
The plate bolts need to be checked for tightness after break-in process and also after each of the first 3 to 4 heat cycles. If they have loosened, tighten to a torque spec of 75 inch pounds. The plate bolts are the torx bolts located at the center of the activator plate (T27 Torx Plus).
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Turbo Bully clutch is preset between .030� and .035�. During break-in it is expected to see the air gap grow approximately .010�. For most applications the clutch will perform at its peak with an air gap between .040� and .055�. When this dimension is greater than .065� the floater disc should be changed to a thicker unit to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .140� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly. The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Check the 6 plate bolts for tightness as part of your weekly clutch maintenance. Tighten to 75 inch pounds if needed. If the Torx bolts need to be removed for disc replacement, use a high temp loc-tite when re-installing.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In an effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
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NOTE:The Bully jackshaft clutch is only intended for use on two-stroke powered competition race karts. It is to be mounted on a 3/4� jackshaft which is geared to run 2.71 times slower than the engine. The proper method of achieving this is to use a 21 tooth belt drive pulley on the engine, and a 57 tooth driven pulley on the jackshaft. The shaft itself needs to be drilled and tapped on one end for the 5/16� fine bolt provided. Sprockets available for the 4 disc clutch run from 14 tooth to 30 tooth. A gear chart is included with the clutch with the ratios for each of these sprockets.
Model Applications - Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. However, with stiff springs and heavy weights, the clutch will have to drop well below its engagement RPM before the clutch will once again release. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds. Below is a chart with the common weight and spring combinations that we recommend on the Bully clutch.
Stall speed.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
The plate bolts need to be checked for tightness after break-in process and also after each of the first 3 to 4 heat cycles. If they have loosened, tighten to a torque spec of 75 inch pounds. The plate bolts are the torx bolts located at the center of the activator plate (T27 Torx Plus).
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Turbo Bully clutch is preset between .030� and .035�. During break-in it is expected to see the air gap grow approximately .010�. For most applications the clutch will perform at its peak with an air gap between .040� and .055�. When this dimension is greater than .065� the floater disc should be changed to a thicker unit to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .140� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly.
The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Check the 6 plate bolts for tightness as part of your weekly clutch maintenance. Tighten to 75 inch pounds if needed. If the Torx bolts need to be removed for disc replacement, use a high temp loc-tite when re-installing.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In an effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
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NOTE:We have found he length of pto crankshafts vary by manufacturer, model and from motor to motor within models. This is an area to pay close attention to, as the length of the crankshaft affects the internal side clearance of the clutch. If needed shim washers and spacers are included. These parts can be used to adjust your side clearance in the range of .010� to .025�. The exploded view of the clutch shows where to position the spacers. In some circumstances it may be necessary to trim the length of the key. In all circumstances the cutaway area of the key must fit under the sprocket bearing.
Model Applications - The 1� Turbo clutch is designed expressly for use on high torque 4 stroke racing engines that utilize a 1� PTO shaft. Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds.
Stall speed.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
The plate bolts need to be checked for tightness after break-in process and also after each of the first 3 to 4 heat cycles. If they have loosened, tighten to a torque spec of 75 inch pounds. The plate bolts are the torx bolts located at the center of the activator plate (T27 Torx Plus).
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Turbo Bully clutch is preset between .030� and .035�. During break-in it is expected to see the air gap grow approximately .010�. For most applications the clutch will perform at its peak with an air gap between .040� and .055�. When this dimension is greater than .065� the floater disc should be changed to a thicker unit to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .140� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly. The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Check the 6 plate bolts for tightness as part of your weekly clutch maintenance. Tighten to 75 inch pounds if needed. If the Torx bolts need to be removed for disc replacement, use a high temp loc-tite when re-installing.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In an effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
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Model Applications - Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. However, with stiff springs and heavy weights, the clutch will have to drop well below its engagement RPM before the clutch will once again release. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds. Below is a chart with the common weight and spring combinations that we recommend on the Bully clutch.
The shaded areas above designate the "basic" weight package. All one disk clutches in the same shade only require spring height adjustments for class changes. The engagement RPM�s found with the spring heights may vary with each individual, and are listed as a reference point only. The actual engagement should be at or up to 200 RPM�s above the peak torque of the engine.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Bully clutch is preset between .030� and .035�. As the friction disk wears, the air gap may increase to the wear limit of .050�. When this dimension is reached a shim located under the activator plate should be removed to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .150� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly.
The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In an effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
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Model Applications - Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. However, with stiff springs and heavy weights, the clutch will have to drop well below its engagement RPM before the clutch will once again release. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds. Below is a chart with the common weight and spring combinations that we recommend on the Bully clutch.
The shaded areas above designate the "basic" weight package. All one disk clutches in the same shade only require spring height adjustments for class changes. The engagement RPM�s found with the spring heights may vary with each individual, and are listed as a reference point only. The actual engagement should be at or up to 200 RPM�s above the peak torque of the engine.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Bully clutch is preset between .030� and .035�. As the friction disk wears, the air gap may increase to the wear limit of .050�. When this dimension is reached a shim located under the activator plate should be removed to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .150� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly.
The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In and effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
|
|
Model Applications - Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. However, with stiff springs and heavy weights, the clutch will have to drop well below its engagement RPM before the clutch will once again release. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds. Below is a chart with the common weight and spring combinations that we recommend on the Bully clutch.
The shaded areas above designate the "basic" weight package. All two disk clutches in the same shade only require spring height adjustments for class changes. The engagement RPM�s found with the spring heights may vary with each individual, and are listed as a reference point only. The actual engagement should be at or up to 200 RPM�s above the peak torque of the engine.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Bully clutch is preset between .030� and .035�. As the friction disk wears, the air gap may increase to the wear limit of .050�. When this dimension is reached a shim located under the activator plate should be removed to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .150� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly.
The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In an effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
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Model Applications - Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. However, with stiff springs and heavy weights, the clutch will have to drop well below its engagement RPM before the clutch will once again release. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds. Below is a chart with the common weight and spring combinations that we recommend on the Bully clutch.
The shaded areas above designate the "basic" weight package. All two disk clutches in the same shade only require spring height adjustments for class changes. The engagement RPM�s found with the spring heights may vary with each individual, and are listed as a reference point only. The actual engagement should be at or up to 200 RPM�s above the peak torque of the engine.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Bully clutch is preset between .030� and .035�. As the friction disk wears, the air gap may increase to the wear limit of .050�. When this dimension is reached a shim located under the activator plate should be removed to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .150� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly.
The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In an effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
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Model Applications - Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. However, with stiff springs and heavy weights, the clutch will have to drop well below its engagement RPM before the clutch will once again release. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds. Below is a chart with the common weight and spring combinations that we recommend on the Bully clutch.
The shaded areas above designate the "basic" weight package. All two disk clutches in the same shade only require spring height adjustments for class changes. The engagement RPM�s found with the spring heights may vary with each individual, and are listed as a reference point only. The actual engagement should be at or up to 200 RPM�s above the peak torque of the engine.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Bully clutch is preset between .030� and .035�. As the friction disk wears, the air gap may increase to the wear limit of .050�. When this dimension is reached a shim located under the activator plate should be removed to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .150� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly.
The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In an effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
|
|
Model Applications - Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. However, with stiff springs and heavy weights, the clutch will have to drop well below its engagement RPM before the clutch will once again release. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds. Below is a chart with the common weight and spring combinations that we recommend on the Bully clutch.
The shaded areas above designate the "basic" weight package. All three disk clutches in the same shade only require spring height adjustments for class changes. The engagement RPM�s found with the spring heights may vary with each individual, and are listed as a reference point only. The actual engagement should be at or up to 200 RPM�s above the peak torque of the engine.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Bully clutch is preset between .030� and .035�. As the friction disk wears, the air gap may increase to the wear limit of .050�. When this dimension is reached a shim located under the activator plate should be removed to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .150� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly.
The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In an effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
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Model Applications - Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. However, with stiff springs and heavy weights, the clutch will have to drop well below its engagement RPM before the clutch will once again release. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds. Below is a chart with the common weight and spring combinations that we recommend on the Bully clutch.
The shaded areas above designate the "basic" weight package. All three disk clutches in the same shade only require spring height adjustments for class changes. The engagement RPM�s found with the spring heights may vary with each individual, and are listed as a reference point only. The actual engagement should be at or up to 200 RPM�s above the peak torque of the engine.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Bully clutch is preset between .030� and .035�. As the friction disk wears, the air gap may increase to the wear limit of .050�. When this dimension is reached a shim located under the activator plate should be removed to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .150� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly.
The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In an effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
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Model Applications - Spring and weight combinations may be interchanged to suit the individual application. As you make your selections be aware that the heavier the weights and the stiffer the spring, the more positive the engagement becomes. However, with stiff springs and heavy weights, the clutch will have to drop well below its engagement RPM before the clutch will once again release. Stiffer springs are springs with a larger wire diameter and they will give higher stall speeds. Below is a chart with the common weight and spring combinations that we recommend on the Bully clutch.
The shaded areas above designate the "basic" weight package. All three disk clutches in the same shade only require spring height adjustments for class changes. The engagement RPM�s found with the spring heights may vary with each individual, and are listed as a reference point only. The actual engagement should be at or up to 200 RPM�s above the peak torque of the engine.
Stall speed is the reading shown on the tach as the kart is accelerating from a slow speed before the clutch has become a locked couple.
As the springs are adjusted clockwise, the tension on the springs is increased and the stall speed is raised. The inverse is true of turning the springs counter clockwise, as this will lower the stall speed.
We have found from extensive testing with a computerized accelerometer that the greatest rate of acceleration will occur when the clutch engages at the torque peak of the motor. However, it also should be pointed out that the addition of the clutch to an engine may change at what RPM your engine produces its torque peak. (Usually it moves up 100 to 200 RPM) Also, a given clutch set up will be most efficient with a given amount of torque and engagement RPM. Figure 3 provides some information for anyone looking to deviate from the above settings.
When setting stall speed we suggest making your adjustments in 1/4 turn increments at a time. When testing for your stall speed, use extreme caution as to not over heat the clutch. Next to contamination of the friction disks, heat is the clutch�s biggest enemy so be sure to let the clutch cool down completely between stall speed tests.
Installation.
When installing the Bully clutch, the drive sprocket should be installed facing toward the engine. Even though the clutch will have equal performance installed in either direction, the life of the aluminum clutch basket will be much shorter if the clutch is installed with the sprocket outward. Additionally, the clutch adjustment springs will be more accessible when the clutch is installed correctly.
When installing your clutch make sure there is a minimum of .015� and maximum of .030� end play. After tightening your clutch to the engine, end play can be checked with a feeler gauge between the end of the drive hub and the crankshaft step. See Figure 1. Reducing end play is done by using the .035� shims included, part # 151-002. If the crankshaft is short it will need to have the end play increased by shimming out the 098-015 aluminum washer against the end of the crankshaft. This can be done by placing a washer against the end of the crankshaft that allows the drive hub to slide over it. Not having enough end play my cause permanent damage to your clutch.
Clutch disc break in.
The clutch discs require a period of break-in in order to achieve maximum clutch performance. During this time the outer surface of the linings becomes hot and the microscopic pores of the lining material will burnish themselves to a stable condition. The friction material used in the manufacture of the Bully clutch discs will cause the discs to have more bite as the clutch gets hot. The bite from the disc will also continue to increase throughout the life of the disc.
The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes.
Air gap.
The air gap is the clearance between the friction disks. It is measured with a common feeler gauge and is stated in thousandths of an inch. When new, the Bully clutch is preset between .030� and .035�. As the friction disk wears, the air gap may increase to the wear limit of .050�. When this dimension is reached a shim located under the activator plate should be removed to restore the air gap back to the original dimension. See Figure 2.
Spring height.
As mentioned earlier, spring height will effect the engagement RPM of the clutch. We suggest making equal adjustments to all 6 springs of 1/4 turn increments at a time. The spring diameter, preload, weight package, engines power and several other variables all will effect how much of an RPM change is found with a 1/4 turn change but an average change will be approximately 100 RPM. Turn the spring adjustment clockwise for more slip and counter clockwise for less slip. The range of adjustment should be between .150� and .330�. This is the distance between the bottom of the spring retaining washer and the top of the activator plate. See Figure 3.
Theory of operation and dialing in the Bully clutch.
For theory sake lets suppose that the outer clutch basket is constrained and not allowed to rotate such as would occur if the brake was held on tight. When the throttle is opened, the engine will come up to a certain RPM, the clutch will engage and a point of equilibrium will be found......At this point of equilibrium, or stall speed, the entire amount of torque being produced by the engine is being transferred into the clutch. What RPM this occurs at is controlled by 4 variables. Namely the weight of the levers, applied tension of the springs, the coefficient of friction between the friction disks and the amount of torque the engine is producing. A change of each of these variables has it�s own unique effect on the engagement quality of the clutch. As a guideline, lighter levers and less spring tension performs best on motors with lower peak torque values and on tracks where the clutch is continually cycled through its slip range. Heavy levers and high spring tensions will perform best on motors with high torque values and on tracks that require a good launch on the start. If levers are too light for the torque available, the clutches point of equilibrium will be inconsistent and the transfer of power will be inefficient. If the clutch has too much weight on the levers, or the coefficient of friction of the discs is too great for the torque of the engine, a chatter will be produced by the clutch. Chatter is an attempt by the clutch to create a complete lock-up. If the engine does not have enough torque to maintain its RPM, the clutch slows.. releases..the engine speeds back up.. and the resultant chatter is from this process repeating itself very rapidly. Chatter, if left unchecked will destroy a clutch in just a matter of minutes.
Spring color and height recommendations.
Our recommended starting points for spring height and lever/weight combinations on a motor with average torque.
What the spring color and height chart cannot allow for is the coefficient of friction available from the friction discs. The amount of friction produced by the discs may vary. The biggest culprit to friction reduction is from contamination of the discs themselves. The most common forms of contamination are chain oil, moisture and dirt. In most instances the clutch discs will run hot enough to burn off most of these contaminates, however, if the discs become contaminated the clutch may lose its positive feel while also losing some of its ability to transfer power. In the real world, friction discs will not always be able to work in an uncontaminated environment. To cure a soft engagement and restore the clutches ability to transfer power you may want to add weight to the levers. Follow this by readjusting your springs IN, clockwise, until your ideal engagement point is once again found.
The other side of the above condition is too much disc friction. This can occur from a very rapid break-in, very low humidity conditions, rust, or when certain cleaners have contaminated the friction discs. This condition will result in a clutch chatter and if left unchecked may cause mechanical damage to the clutch. To cure a chatter, first remove weight from the levers (if present). If all of the weight is removed from the levers and a chatter is still present, check all springs to insure equal spring height settings.
MAINTENANCE.
The clutch should be protected from moisture and dirt as much as possible. It is important that a small amount of lubrication is provided to the chain. However, too much lubrication can cause the lubricant to migrate to the friction disks and render them useless. So, oil the chain sparingly.
The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, re-lube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch.
The thrust bearing located in between the sprocket and the clutch hub should be run dry. Of course its life would be extended by lubricating it, but the lubrication from this bearing is most likely to contaminate the friction discs. Since the price of replacing the thrust bearing is very low compared to the price of friction discs, we recommend that this bearing be run dry. The friction disks should be replaced when their thickness becomes less than .110� or when the square outer drive prongs become deformed. A chatter condition in the clutch will cause almost immediate damage to the friction disk drive prongs and the basket.
The pressure plate and the clutch hub should periodically be checked for warpage and straightness. If in doubt, they should be re-ground or replaced.
Levers require visual inspection each time the clutch is disassembled. Look for flat spots developing on the nose of the lever. By the nose, we are referring to where the lever contacts the pressure plate. If any noticeable wear is seen, the lever should be replaced. Also make sure that the lever is able to rotate freely on the dowel pin.
Important sprocket information.
Bully Sprockets are manufactured using the highest grade of materials, CNC machining and heat treat processing. In an effort to give your sprocket the best life expectancy and performance, we offer the following tips.
The sprocket has a removable needle bearing specially designed for applications with minimal lubrication. A small amount of lubricant should be applied to the bearing prior to installation but if you can see the lube on the needle rollers, you have probably used too much. Since oil and other contaminants can migrate to the friction discs, reducing their life expectancy and engagement quality, we recommend using petroleum jelly to lubricate the bearing. It will vaporise at relatively low temperatures but will provide enough lubrication for acceptable bearing life.
When installing the sprocket in the basket, be sure to use the LARGE snap ring, part # 098-028. To prevent the snap ring from rotating the screw (ZN-93724) MUST BE INSTALLED BETWEEN THE SNAP RING ENDS. The included outer washer (098-013) is to be installed between the sprocket and the drive hub snap ring. Side clearance should be between .010� and .030� when measure with a feeler gauge. See Figure 4.
Do not use any aftermarket sprockets with a bronze bushing. Use of any aftermarket sprocket may effect performance and fit of the Bully clutch. Caution: Clutch damage caused by aftermarket parts is the responsibility of the consumer.
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You will find this gauge to be very helpful in accurately setting the spring heights of your disk clutch. The gauges are pre calibrated at the factory for the Bully clutch. If you wish to check the calibration, or wish to re-calibrate the gauge for use on another brand of clutch, follow the instructions below. To calibrate your gauge: Locate the tallest knurled knob (it is found on the top of the indicators shaft) and turn it counterclockwise until the needle on the small dial will go to the left of its zero point and the large needle is pointing straight down. Next loosen the short knurled nut that holds the face plate in position. Then set bottom of the gauge on a flat surface and turn the face until the needle lines up with the red number 40. This method takes into account the .040" thickness of the Bully spring retainer. On other brands of clutches you will need to measure the thickness of the spring retainer in thousands of an inch and substitute that dimension for the 40 in our example. Horstman�s are generally around .065". Jammer clutches may vary from Horstman�s. For complete accuracy measure your individual clutches retaining washers. Retighten both knurled nuts, and the gauge is calibrated. NOTE�..The gauge indicates the highest point on the TOP of each spring retaining washer. When reading the gauge, first look at the small dial inside the larger dial. This dial reads in 1/100ths of an inch. Next to read tenths and 1/1000 of an inch, look at the large dial and read the black numbers. On the Bully clutch, � of a turn of all six screws will equal approximately 125 RPM; this equates to about .010" on the gauge. On an MDC-400 clutch, � of a turn of the screw will equal 100 RPM. This equates to about.007" on the gauge. Many clutches are inconsistent on their spring heights; variances of .060" are common. On a four-stroke clutch, this can mean a difference of 750 RPM on the stall speed of a clutch. Chatter, warping, slippage of the friction disks and damage to the lever support plate, can all result from miss adjustment. We suggest all of the spring heights be adjusted to within at least .004� of each other. If you are satisfied with your clutch�s engagement rpms, but the springs are at varying heights, check the spring heights with the gauge and record them. If they are inconsistent more than .002", add all of the readings together and divide the sum by the number of springs on the clutch. This will give you the average spring height. If the springs are then reset to this reading the clutch engagement will remain at the same rpm.
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The following are a few additional steps and precautions that are intended to help you get the most life and performance out of your new clutch. BREAK-IN The method of break-in that is preferred is one where the clutch is slipped for short periods and then time is allowed for the heat to dissipate evenly throughout the clutch. The break in process should be done when the clutch is new and also after each time the clutch is disassembled or rebuilt. This can be done with the kart on the stand. The break in process of the clutch is similar to the break in of your motor after it has been rebuilt. The goal of the process is to gradually build temp in the clutch at short intervals with cooling between the intervals. If you have a tire temp gun it works great for this process. Engage the clutch and bring the temp up to about 250 degrees and then allow it to cool down, engage the clutch again and bring the temp up to about 300 degrees and again allow it to cool down. Continue this process until you bring the clutch up to approximately 400 degrees. This entire process should take about 4 to 5 minutes. Break in can also be done on parade laps on an oval track. The clutch is slipped for short periods and then time is allowed for the heat to dissipate evenly throughout the clutch, gradually increasing the heat. One or two sessions on the track like this will do a good job of break-in. DISK CONTAMINANTS The friction material that is used in the construction of the BULLY disk is porous, and it will attract liquids somewhat like a sponge. Any liquid that comes in contact with the friction surface should be considered a contaminant. The very worst of these is ant�friction additives as well as the oils or greases that carry them. The smallest amount, just a drop the size of a pinhead, will cause irreversible damage to the friction surface. Some of these additives will even permeate the metal friction surfaces. Repair involves not only replacement of the friction disks but also re-grinding all of the friction surfaces in the clutch. The main source for these contaminants is chain oils, engine oils, and grease migrating from the sprocket bearing. When compared to the friction disks the sprocket bearing is a relatively inexpensive item to replace. We recommend that this bearing be run with as little lubricant as possible. DISK WEAR The friction material in the BULLY clutch will actually gain bite and have a better transfer of energy when the disks get some heat in them. If there are no parade laps, a slight amount of preheating the disks on the grid may help improve your starts. The friction material will actually gain bite as it goes through these heat cycles and wears. This means that as long as you keep contaminants off of the friction surfaces, the clutch will actually improve with use. BASKET WEAR On the aluminum baskets, the surface where the disk tang transfers its force will wear quickly to the steel dowel pin. After this initial wear in occurs, the disk will be contacting the steel surface of the dowel pin. The disk will then wear to the shape of the dowel pin, and from this point on the wear will be minimal. BLUEPRINTING There are many different processes that are referred to as "blueprinting". Normally the intent is to bring all of the clutch�s components up to the ideal factory dimensions. The friction surfaces of the BULLY clutch are manufactured to extremely close tolerances. Many times the person blueprinting the clutch will simply not have tools to hold tolerances as closely as the factory. So before you allow someone to "blueprint" your clutch please make sure that they have equipment capable of doing the job correctly. At times racers feel that the friction surfaces need to be scuffed with sandpaper. This may give a little more bite for one or two outings, but the sanding will have completely destroyed the flatness of the surfaces. From this point on the performance will very quickly deteriorate. If more bite in the clutch is desired, first make sure that the clutch disks have not been contaminated. If the disks are OK, then the correct solution would be to add weight to the levers. CLEANING The clutch should be cleaned after each race night. To clean your clutch we recommend taking the sprocket/ basket assembly off the clutch. Take the 2 pieces and soak them in a bath of acetone for about 10 minutes. After soaking, spray the clutch out with air, relube the sprocket bearing with a small amount of Vaseline and reinstall on the motor. Periodically the air gap and disc thickness should be checked but we do not recommend disassembling the clutch except to change the air gap or rebuild the clutch. Our recommendation is to NEVER sand the disc and when disassembling to change the air gap, we recommend that you mark the clutch so all pieces go back together in the same location.
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REBUILDING - After a period of time it becomes necessary to re-build the clutch. Here are some guidelines on how to deal with the friction surfaces.
1. Whenever the friction discs are replaced it is important that all of the matching friction surfaces be either re-ground, or replaced. These surfaces rely on the cross hatch pattern ground on their surfaces to properly break-in a new set of friction discs. If the proper surface finish is not present, the contact between the surfaces will never become as intended and performance will suffer.
2. If the steel friction surfaces are re-ground the process must not only result in a proper cross hatch, but also the finished surface must be completely flat.
3. NEVER, EVER, use sand paper to rough-up or deglaze the surfaces. This method simply cannot keep the surfaces flat enough nor can it provide the proper cross hatching. It will however provide some �teeth� for the friction material to bite into, and may at first seem to make a feeble clutch perform better. However, after the initial roughness has worn off the clutch will perform worse than it did before the treatment. (The initial roughness from coarse sanding usually takes 1 to 3 starts to be worn away)
4. If the decision is made to have the clutch �Blueprinted� be sure that you deal with a reputable blueprinter. Many shops that offer clutch blueprinting simply do not have the equipment to properly do the job or test the results. Others do little more than set the spring heights and air gap, and send a large bill. With that being said there are also some very good craftsmen blueprinting clutches. Make sure you know who you are dealing with.
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Supplemental instructions for the new style sprockets (2003 and later) To combat bushing and bearing slippage, the Bully clutch sprockets have been redesigned. The 12�s and 13�s now have a bushing retaining ring in the base of the sprocket. To make room for this ring, the base of the sprocket was thickened, and the standard thrust washers (part #098-112) have been replaced with the new #098-113 thin thrust washers. To use this bushing retaining ring, the 12 or 13 tooth sprocket should be pressed into the drum first, and then the ring may be installed. To change sprockets, first remove the ring, then push the sprocket out of the drum. The 14 through 21t Bully sprockets also use the new retaining ring to prevent the bearing from slipping out of the sprocket. The sprocket also has a "lip" in the base to prevent the bearing from slipping inward toward the clutch. These sprockets also have been thickened, and require the use of the new #098-113 thin thrust washers.* In addition, it is now necessary to always use the #098-013 outer thrust washer with these sprockets. It will seat down nicely on the bearing retaining ring, and allow the proper amount of endplay. These instructions also apply to the 15, 16 and 17 "skip tooth" sprockets as well. Bully bushing type sprockets (12 and 13 tooth) use a bushing of bronze material. Use of other sprocket brands with a brass bushing may cause immediate and catastrophic failure of the Bully clutch. Damage to the Bully clutch caused by the use of a sprocket with a brass bushing is the responsibility of the consumer.
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When compared to the larger sprocket sizes, the 11-tooth sprocket is very thin and fragile, making its life span much shorter. High BHP and high torque applications may make the life span unacceptably short. Due to the fragility of the part it should be treated with more care than the larger sized sprockets. We suggest that you polish the surface of the drive hub�s bearing sleeve with 600 grit wet/dry sandpaper to as smooth a surface as possible. Also sparingly apply a light coating of heavy weight wheel bearing grease to the inside of the sprocket. Then take it apart and clean and re-grease it after each run. The 11 tooth sprocket uses a different outer snap ring (098-003) and washer(098-026) which is exclusive to the 11 tooth. These parts are included with the purchase of the 11 tooth sprocket. 
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