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 InspectionCaliper Fluid Seal Damage
The fluid seal (piston seal) [A] is placed around the piston
to maintain clearance between the pad and the disc. If
the seal is in a poor condition, it could lead the pad to wear
excessively or the brake to drag, which may cause the temperature
of the discs or the brake fluid to increase.
Re ...
Clutch Plate, Wear, Damage Inspection
Visually inspect the friction and steel plates for signs of
seizure, overheating (discoloration), or uneven wear.
Measure the thickness of each friction plate [A] at several
points.
If any plates show signs of damage, or if they have worn
past the service limit, replace them with new on ...
Information for Coolant
To protect the cooling system (consisting
of the aluminum engine and
radiator) from rust and corrosion, the
use of corrosion and rust inhibitor
chemicals in the coolant is essential. If
coolant containing corrosion and rust
inhibitor chemicals are not used, over
a period of time, the cooling ...