When is the last time the springs in the primary and secondary have been replaced?
Sometimes a good cleaning and new springs is all that is necessary to regain lost performance. Remove the clutch, take the cover off and clean, and examine for any bad rollers, weight bushings, or main bushing. Clutches wear slowly, and as they wear, performance diminishes just as slowly. You don't realize you have lost any performance until replacing the old, worn parts.
Check the ramp and buttons (if Polaris secondary) for wear too.