If there are notches worn into the splines, replace the sub clutch hub. Also, replace the steel plates if their teeth are damaged.

Clutch Housing Finger Inspection
Damper Cam InspectionSpring Plate Free Play Adjustment
NOTE
The free play adjustment is performed by replacing the
steel plate(s).
Measure the clutch spring plate free play (see Clutch
Spring Plate Free Play Measurement), and then replace
the steel plate(s) which brings the free play within the
usable range.
Spring Plate Free Play
Usable ...
Engine Oil
In order for the engine, transmission,
and clutch to function properly, maintain
the engine oil at the proper level,
and change the oil and replace the oil
filter in accordance with the Periodic
Maintenance Chart. Not only do dirt
and metal particles collect in the oil, but
the oil itself los ...
Cylinder (Upper Crankcase) Wear Inspection
Split the crankcase (see Crankcase Splitting).
Remove the pistons (see Piston Removal).
Assemble the cylinder (upper crankcase) [A], the cylinder
head [B] and the cylinder head gasket [C].
Tighten the cylinder head bolts (see Cylinder Head Installation
in the Engine Top End chapter).
...