Clutch Break-in & Maintenance

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.