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 DiscDFI System Wiring Diagram (KIBS Equipped Models)
1. Air Intake Solenoid Valve (Other than US, CA and CAL Models)
2. Engine Stop Switch
3. Starter Button
4. Air Switching Valve
5. Stick Coil #1, #2, #3, #4
6. Spark Plugs
7. Intake Air Temperature Sensor
8. Crankshaft Sensor
9. Secondary Fuel Injector #1
10. Secondary Fuel Injector #2
...
Swingarm Bearing Removal
Remove:
Swingarm (see Swingarm Removal)
Collar [A]
Oil Seals [B]
Sleeve [C]
Circlip [D] (Right Side)
Special Tool - Inside Circlip Pliers: 57001-143
Remove the ball bearing and needle bearings.
Special Tool - Oil Seal & Bearing Remover [A]: 57001-1058
...
Regulator/Rectifier Inspection
Remove:
Upper Fairing Assembly (see Upper Fairing Assembly
Removal in the Frame chapter)
Right Inner Fairing (see Inner Fairing Removal in the
Frame chapter)
Bolts [A]
Regulator/Rectifier [B]
Set the hand tester to the × 1 kΩ range and make the
measurements show ...