The key clutch is an advanced sort of centrifugal clutch and is often mounted to the output stop on the motor crankshaft. The clutch has two sheave faces; one which is laterally set (stationary sheave), and one which can move out and in to engage the belt (moveable sheave). https://gearboxcvt98631.suomiblog.com/detailed-notes-on-gearbox-cvt-48015631