The primary clutch is an advanced form of centrifugal clutch and is often mounted into the output stop of the motor crankshaft. The clutch has two sheave faces; one that is laterally fixed (stationary sheave), and one which can transfer out and in to interact the belt (moveable sheave). https://holdenonkik.anchor-blog.com/12627174/gearbox-cvt-things-to-know-before-you-buy