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 DiscWater Pump Housing Disassembly
NOTICE
Do not damage the hole wall of the water pump
housing.
Insert a bar [A] into the pump housing [B], and hammer
evenly around the circumference of the mechanical seal
bottom [C].
Take the oil seal [A] out of the housing [B] with a hook [C].
...
Exhaust Butterfly Valve Actuator Sensor Output Voltage Inspection
NOTE
Before this inspection, confirm the pulley is original
position (see Exhaust Butterfly Valve Actuator Installation).
Disconnect:
3 Pins Connector [A] (see Exhaust Butterfly Valve Actuator
Sensor Output Voltage Inspection)
2 Pins Connector [B]
Connect the harness adapter [A ...
Throttle Control System Inspection
Check the throttle grip free play [A].
If the free play is incorrect, adjust the throttle cables.
Throttle Grip Free Play
Standard: 2 3 mm (0.08
0.12 in.)
Check that the throttle grip [B] moves smoothly from full
open to close, and the throttle closes quickly and completely
by the ...