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 DiscSwingarm 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 ...
Upper Crankcase Assembly
When installing the breather plate, replace the gasket [A]
with a new one.
Apply a non-permanent locking agent to the threads of
the bolts [A] and tighten them.
Torque - Breather Plate Bolts: 9.8 N·m (1.0 kgf·m, 87 in·lb)
Install the fitting [A] until it is bottomed ...
Subthrottle Valve Actuator Resistance Inspection
Turn the ignition switch to OFF.
Disconnect the subthrottle valve actuator connector [A].
Connect a digital meter to the subthrottle valve actuator
connector [A].
Measure the subthrottle valve actuator resistance.
Subthrottle Valve Actuator Resistance
Connections: Y/BK lead [1 ...