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 DiscIgnition System
WARNINGThe ignition system produces extremely
high voltage.
Do not touch the spark plug, ignition coil or ignition
coil lead while the engine is running, or you
could receive a severe electrical shock.
NOTICE
Do not disconnect the battery cables or any other
electrical ...
Fuel Reserve Switch Inspection
Fill the fuel tank with fuel and close the fuel tank cap.
Remove the front seat (see Front Seat Removal in the
Frame chapter).
Disconnect the fuel pump lead connector [A].
Connect the test light [A] (12 V 3.4 W bulb in a socket
with leads) and the 12 V battery [B] to the fuel pu ...
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.
...