STM Slipper Clutch: Evoluzione (M25) -1098 / 1198 / SF
The Evolution Slipper Clutch was the very first slipper clutch to utilize a Diaphragm spring! Of course the Evolution uses STM staples like 'Ball & Ramp' actuation for smooth slipper clutch operation, and the STM exclusive 'PEP' - Progressive Engagement Plate to decrease the abruptness during closing of the clutch. In addition, it uses a 90mm Diaphragm Primary Spring and an 85mm Diaphragm Secondary Spring. By using diaphragm springs in both the primary and secondary .. the Evolution Slipper Clutch offers superior adjustability to suit any riding style and engine modification. The primary spring controls the pressure on the clutch pack during lock up.
STM 90mm diaphragm primary springs are weighted in Kilograms and offered in 10Kg increments. There are 9 different weights to choose from (sold individually). Through the use of varying weights, the engine builder can adjust the amount of pressure on the clutch pack to compensate for any engine modifications and subsequent increases in horsepower. The secondary spring is what controls the amount of engine brake. The lighter the secondary spring, the less engine brake; the heavier the secondary spring, the more engine brake.
The 85mm diaphragm secondary springs are weighted in Kilograms and offered in 10Kg increments. There are 6 different weights to choose from (sold individually). Through the use of varying weights, the rider can adjust the amount of engine brake desired to fit their individual riding style.