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 InspectionPrecautions
There are a number of important precautions that are
musts when servicing electrical systems. Learn and observe
all the rules below.
Do not reverse the battery cable connections. This will
burn out the diodes on the electrical parts.
Always check battery condition before condemning other
...
Spring 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 ...
Seat Cover Removal
Remove:
Rear Seat (see Rear Seat Removal)
Remove the bolts [A].
Remove the upper seat cover backward [B] to clear the
hook portions.
Remove:
Front Seat (see Front Seat Removal)
Quick Rivets [A]
Bolts [B]
Seat Covers [C]
...