Originally Posted by afm

Lets review some of theory behind Centax clutches, and from there a practical example, which i hope helps....


Clutch gap is the amount that the clutch shoe moves before it contacts the clutch housing; this affects the WAY that the clutch engages more so than WHEN it engages.

1.- Larger clutch gap: Causes a harder, more sudden engagement. Better on a wider track or a track with high traction. A larger clutch gap puts excess stress on the clutch components, especially the thrust bearing.

2.- Smaller clutch gap: Gives a softer engagement, and smoother acceleration. Better on a tighter track or a track with low traction. A smaller clutch gap may result in engine bogging and premature clutch shoe wear.
If you change the clutch gap to a larger or smaller value (by adjusting the shimming), you must compensate by adjusting the tension on the main clutch tension spring.

End Play Clutch housing end play is the amount that the clutch housing moves along the crankshaft.

1.-Too much end play: Causes more wear on the thrust bearing. When the clutch is not engaged, the plates of the thrust bearing are further apart. When the clutch engages, the thrust bearing plates travel further before they are 'sandwiched' together... by traveling further more force is built up so when the clutch engages, the thrust bearing has more force applied to it. This causes premature thrust bearing wear and leads to failure.

2.-Too little end play (or none at all): means that the thrust bearing spends most of its time sandwiched together, which may lead to overheating and premature wear.

It is always better to have a small amount of end play rather than a larger amount of end play. Do not set up the clutch to have no end play at all.

Since our Centax clutches transform Centrifugal force into Axial force (thus it’s name), if you use lighter flyweights which operate under the centrifugal force, you will need more rpm’s to have them expand, so actually you are getting a later engament, and if you use a harder tension spring, even more later engament and slippage (also depending on how much tension adjustment you placed on the spring). The opposite is true for heavier flyweights and softer spring.

All above being said, the clutch adjustment depends on where the power band and torque of your engine is.
For example: my OS TZ .12 has it’s max torque at around 20,000rpm and it’s max hp at 33, 400rpm
So I need to set my clutch at around the engine’s max torque. If I set the clutch above the 20K mark, engines revs up and makes clutch to slip and heat up because I’m not using the max force of engine to make clutch engage, if I set it up at a lower rpm (below 20K), engine bogs and heats up….

Resuming: one has to set up the clutch to wherever the engines max torque is to use its usable power and make the clutch engage solidly without to much slippage and / or bog.

AFM