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 DiscStick Coil Primary Peak Voltage Inspection
NOTE
Be sure the battery is fully charged.
Remove the stick coils (see Stick Coil Removal).
Do not remove the spark plugs.
Connect the ECU to the harness.
Measure the primary peak voltage as follows.
Install the new spark plug [A] into each stick coil [B], and
ground them onto ...
Spring Tension Inspection
Since a spring becomes shorter as it weakens, check its
free length [A] to determine its condition.
If the spring of either fork leg is shorter than the service
limit, it must be replaced. If the length of a replacement
spring and that of the remaining spring vary greatly, the
remaining s ...
Before Servicing
Before starting to perform an inspection service or carry out a disassembly
and reassembly operation
on a motorcycle, read the precautions given below. To facilitate actual
operations, notes, illustrations,
photographs, cautions, and detailed descriptions have been included in each
chapter w ...