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 DiscCoupling Bearing Inspection
Since the coupling bearing is made to extremely close
tolerances, the clearance can not normally be measured.
NOTE
It is not necessary to remove the coupling bearing for
inspection. If the bearing is removed, it will need to be
replaced with a new one.
Turn the bearing in the coupling b ...
Sidestand Switch Operation Inspection
Raise the rear wheel off the ground with the stand (see
Rear Wheel Removal in the Wheels/Tires chapter).
Inspect the sidestand switch [A] operation accordance to
below table.
Sidestand Switch Operation
If the sidestand switch operation does not work, inspect
or replace the foll ...
Piston Ring End Gap Inspection
Place the piston ring [A] inside the cylinder (upper
crankcase), using the piston to locate the ring squarely
in place. Set it close to the bottom of the cylinder, where
cylinder wear is low.
Measure the gap [B] between the ends of the ring with a
thickness gauge.
Piston Ring End Gap ...