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 Temperature Sensor Output Voltage Inspection
NOTE
Be sure the battery is fully charged.
Turn the ignition switch to OFF.
Remove the throttle body assy (see Throttle Body Assy
Removal in the Fuel System (DFI) chapter).
Disconnect the water temperature sensor connector and
connect the measuring adapter [A] between these connectors
...
Exhaust System Identification
Exhaust Pipe Mark Position [A]
Premuffler Chamber Mark Position [A]
Muffler Body Mark Position [A]
Premuffler Chamber [A] with Hole [B] for Oxygen Sensor [C]
Honeycomb Type Catalyst Position [A]
Specifications
...
Air Intake Duct Removal
Remove:
Upper Fairing Assembly (see Upper Fairing Assembly
Removal in the Frame chapter)
Meter Bracket (see Meter Unit Removal/Installation in
the Electrical System chapter)
Immobilizer Amplifier [A] (Equipped Models) (see Immobilizer
System Parts Replacement in the Electrical System
...