If a master cylinder or piston shows any damage, replace them.

If a cup is worn, damaged softened (rotted), or swollen, the piston assembly should be replaced to renew the cups.
If fluid leakage is noted at the brake lever, the piston assembly should be replaced to renew the cups.
If they are damaged, replace them.
If the springs are damaged, replace them.
If the relief port becomes plugged, the brake pads will drag on the disc. Blow the ports clean with compressed air.
Front Master Cylinder [I] Rear Master Cylinder [J]

Rear Master Cylinder Installation
Brake DiscBrake Hose and Pipe Damage and Installation Condition Inspection
Inspect the brake hoses, pipes and fittings for deterioration,
cracks and signs of leakage.
The high pressure inside the brake line can cause fluid to
leak [A] or the hose to burst if the line is not properly maintained.
Bend and twist the rubber hose while examining
it.
Replace the ...
Exhaust Butterfly Valve Cable Installation
Confirm whether pulley [A] is an angle shown in the figure.
41.7° ±7° [B]
This position is original position of the pulley.
NOTE
Correct the position electrically after confirming the use
is discontinued and there is no damage when differing
from the angle of shown in the figure.
...
Steering Stem Warp Inspection
Whenever the steering stem is removed, or if the steering
can not be adjusted for smooth action, check the steering
stem for straightness.
If the steering stem [A] is bent, replace the steering stem.
Stem Cap Deterioration, Damage Inspection
Replace the stem cap if its oil seal [A] s ...