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 DiscRear Sprocket Removal
Remove the rear wheel (see Rear Wheel Removal in the
Wheels/Tires chapter).
NOTICE
Do not lay the wheel on the ground with the disc
facing down. This can damage or warp the disc.
Place blocks under the wheel so that the disc does
not touch the ground.
Remove:
Rear Sprocket Nu ...
Stick Coil Removal
Remove the air cleaner housing (see Air Cleaner Housing
Removal in the Fuel System (DFI) chapter).
Disconnect the stick coil connectors [A].
Pull out the stick coils [B] upward.
First, turn the stick coil by 90 degrees, and then pull it out
by twisting the coil head to the left and righ ...
Crankcase Assembly
NOTICE
The upper and lower crankcase halves are machined
at the factory in the assembled state, so the
crankcase halves must be replaced as a set.
With a high flash-point solvent, clean off the mating surfaces
of the crankcase halves and wipe dry
WARNINGGasoline and low flash-poin ...