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 InspectionLights and Switches Operation Inspection
First Step
Set the gear position in the neutral position.
Turn the ignition switch to ON.
The following lights should go on according to below table.
If the following light does not go on, inspect the meter
unit (see Meter Unit Inspection in the Electrical System
chapter).
...
Throttle Control System
Check the throttle grip play each day
before riding the motorcycle, and carry
out maintenance and adjustments in
accordance with the Periodic Maintenance
Chart. Adjust it if necessary.
Throttle Grip
The throttle grip controls the butterfly
valves in the throttle body. If the throttle
grip ha ...
Valve-to-Guide Clearance Measurement (Wobble Method)
If a small bore gauge is not available, inspect the valve
guide wear by measuring the valve to valve guide clearance
with the wobble method as indicated below.
Insert a new valve [A] into the guide [B] and set a dial
gauge against the stem perpendicular to it as close as
possible to the cy ...