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 DiscCamshaft, Camshaft Cap Wear Inspection
Remove the camshaft caps (see Camshaft Removal).
Cut the strips of plastigage (press gauge) to journal width.
Place a strip on each journal parallel to the camshaft installed
in the correct position.
Tighten the camshaft cap bolts and upper camshaft chain
guide bolts to the specified ...
Swingarm Bearing Installation
Replace the needle bearings, ball bearing, grease seals
and circlip with new ones.
Install the needle bearings, ball bearing, grease seals and
circlip as shown in the figure.
Insert the needle bearing driver [A] into the needle bearing
[B] and press the needle bearing into the housing u ...
Fuse Inspection
Remove the fuse.
Inspect the fuse element.
If it is blown out, replace the fuse. Before replacing a
blown fuse, always check the amperage in the affected
circuit. If the amperage is equal to or greater than the
fuse rating, check the wiring and related components for
a short circuit.
...