Clutch bell side of an Evo two speed transmission
Clutch shoes on an Active 50
A centrifugal clutch is a drive engagement mechanism which automatically engages a drive transmission at a certain RPM level. This allows the engine to idle without spinning the wheels.
How it works[]
The design of a centrifugal clutch is relatively straightforward. It operates on the concept of centrifugal force. Attached to the engine's drive shaft are two weights with friction pads on them.
While the engine is running the output shaft is spinning and this spinning throws the shoes outward against a clutch bell. A spring is fitted to hold the clutch shoes in place until the RPM designated for engagement.
A weaker spring/heavier shoes will cause the clutch to engage at a lower RPM while a stronger spring/lighter shoes will cause the clutch to engage at a higher RPM. The higher the RPM that the clutch engages, the more power will be sent to the wheels initially. Increasing engagement RPM will also increase clutch shoe wear rates.