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 InspectionTire Tread Wear Inspection
As the tire tread wears down, the tire becomes more susceptible
to puncture and failure. An accepted estimate is
that 90% of all tire failures occur during the last 10% of tread
life (90% worn). So it is false economy and unsafe to use
the tires until they are bald.
Measure the tread depth a ...
Clutch Removal
Remove:
Clutch Cover (see Clutch Cover Removal)
Clutch Spring Bolts [A]
Clutch Springs (with Clutch Spring Holders)
Clutch Spring Plate [B]
Pusher [C]
Remove:
Friction Plates (10) [A]
Steel Plates (9) [B]
Spring [C]
Spring Seat [D]
Hold the sub clutch hub [A] ...
Air Suction Valve Installation
Install the air suction valve so that opening [A] of the reed
faces downward.
Apply a non-permanent locking agent to the threads of
the air suction valve cover bolts [A], and tighten them.
Torque - Air Suction Valve Cover Bolts: 9.8 N·m (1.0 kgf·m,
87 in·lb)
...