have you tried adjusting the clutch? The adjustor is located on the front cover of the motor above the front driveshaft. Here is an old post by HM for adjusting it.
QUOTE ("Honda Mechanic":tjyr6l4a)
[/quote]Loosen the clutch adjusting screw lock nut. Slowly turn the adjusting screw counterclockwise until resistance is felt. Then turn the adjusting screw clockwise 1/4 turn, and tighten the lock nut to the
TORQUE: 22 N-m (2.2 kgf-m, 16 lb.ft)
After adjustment, start the engine and check for proper clutch operation.