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 InspectionAlternator Rotor Installation
Using a cleaning fluid, clean off any oil or dirt on the following
portions and dry them with a clean cloth.
Crankshaft Tapered Portion [A]
Alternator Rotor Tapered Portion [B]
Install the alternator rotor.
Using a cleaning fluid, clean off any oil or dirt on the
washer [A] ...
Drive Chain Slack Adjustment
Remove the cotter pin [A], and loosen the rear axle nut
[B].
Loosen the both chain adjuster locknuts [C].
If the chain is too loose, turn out the left and right chain
adjusters [D] evenly.
If the chain is too tight, turn in the left and right chain
adjusters evenly, and kick the wheel f ...
Air Switching Valve
Air Switching Valve Operation Test
Refer to the Air Suction System Damage Inspection in the
Periodic Maintenance chapter.
Air Switching Valve Unit Test
Remove the air switching valve (see Air Switching Valve
Removal in the Engine Top End chapter).
Set the hand tester [A] to the × 1 ...