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 DiscOil Cooler Installation
Replace the O-ring [A] with a new one.
Apply grease to the new O-ring.
Install the water hoses and hose clamps [A] as shown in
the figure.
Water Hose (About 300 mm, 11.8 in.) [B]
Water Hose (About 130 mm, 5.1 in.) [C]
Yellow Paint [D]
Tighten:
Torque - Water Hose Clamp S ...
Oil Pump Removal
Remove:
Coolant (Drain, see Coolant Change in the Periodic
Maintenance chapter)
Engine Oil (Drain, see Engine Oil Change in the Periodic
Maintenance chapter)
Sidestand Switch Lead Connector [A] (Disconnect)
Bolt [B] and Water Pipe [C]
Water Pump Cover Bolts [D]
Water Pump Cover [E ...
Windshield
Windshield Removal
Remove:
Bolts [A] and Washers
Windshield [B]
Windshield Installation
Be sure to install the wellnuts [A] and the washers.
Tighten:
Torque - Windshield Mounting Bolts: 1.2 N·m (0.12 kgf·m,
11 in·lb)
...