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 DiscRegulator/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 ...
Air Intake Duct Disassembly
(Other than US, CA and CAL Models)
Remove:
Air Intake Duct (see Air Intake Duct Removal)
Seal [A] and Screen [B]
Turn the air intake valve actuator [C] counterclockwise
(90В°).
Remove the shaft [A] of the air intake valve actuator.
Remove:
Pad [A]
Screws [B]
Air Intake Valve [C]
...
Moving Off
Check that the side stand is up.
Pull in the clutch lever.
Shift into 1st gear.
Open the throttle a little, and start to
let out the clutch lever very slowly.
As the clutch starts to engage, open
the throttle a littlemore, giving the engine
just enough fuel to keep it from
stallin ...