2012 Sportsman 400/500 and EFI Tractor Service Manual 9923412, Page 215Get this manual
CLUTCHING Drive Clutch Operation
Drive clutches primarily sense engine RPMThe two major components which control its shifting function are the shift weights and the coil springWhenever engine RPM is increased, centrifugal force is created, causing the shift weights to push against rollers on the moveable sheave, which is held open by coil spring preloadWhen this force becomes higher than the preload in the spring, the outer sheave moves inward and contacts the drive beltThis motion pinches the drive belt between the spinning sheaves and causes it to rotate, which in turn rotates the driven clutchAt lower RPM, the drive belt rotates low in the drive clutch sheavesAs engine RPM increases, centrifugal force causes the drive belt to be forced upward on drive clutch sheaves