| Too few plates and the friction side of the pressure plate contacts the clutch driven drum , and no amount of spring pressure will bind the drum; clutch will slip and burnout.
Too many plates and on clutch lift the pressure plate splines ( if the clutch has them) may disengage the drum, and depending on the clutch the lift balls may come out off the ramps and jam the floating hub; thus stopping the pressure plate from loading the plates and locking the clutch; result clutch slip.
Slipper clutches are all about thhe amount of gap in an assembled clutch between the pressure plate and the clutch inner drum end surface (axail gap) I think yoyodyne sell clutch shims, (various thickness driven plates) to allow the fine tuning of the clutch operation.Pull the back wheel backwards to lock the clutch then measure the distance from the out side of the pressure plate to the end of the floating drum record (freqently possible through holes in the outer pressure plate that line up with the end of the drum)measurement,then remove 4x plate sets reassemble clutch, snap wheel backwards and measure , record , this last reading is the minimum pack thickness that will allow the springs to lock the clutch . subtract the two measurements and the arrived at distance is the total amount of wear (thickness) the plate pack can sustain before clutch slip.adjust total plate pack thickness untill you like the way it works; clutches also come with different ramp angles which change the unlocking characteristics , as does the star spring,I like the clutches to transmit a fair amount of back -torque to ensure recovery from high-speed high angle wheelies when the air stream starts providing unanticipated lift ,and the back torque is what gently brings the bike down, if i muff the rear brake  |