How you adjust the clutch cable matters. Clutch Adjustment & Clutch Cable Replacement Procedure Having said that, I agree about perhaps needing new friction plates. One simple test is to get on the highway in fifth, then shift down to third as if you were going to pass a car. Any clutch slippage will become quite obvious at that point. Do that test after adjusting the cable. If there is no slippage of the clutch, and the cable adjustment does not remedy the engagement problem, then you most likely need a new clutch cable. They do stretch a bit, and a bit is enough to keep the clutch from fully disengaging.