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 DiscBattery Ground
Before completing any service on the motorcycle, disconnect
the battery cables from the battery to prevent the engine
from accidentally turning over. Disconnect the ground
cable (–) first and then the positive (+). When completed
with the service, first connect the positive (+) cable to the
p ...
Exploded View
AL: Tighten the two clamp bolts alternately two times to ensure even
tightening torque.
G: Apply grease.
R: Replacement Parts
G: Apply grease.
L: Apply a non-permanent locking agent.
R: Replacement Parts
Specifications
...
Nozzle Assy Assembly
Before assembling, blow away dirt or dust from the delivery
pipes [A] by applying compressed air [B].
Replace the O-rings [A] of the joint pipe [B] with new ones.
Apply engine oil to the new O-rings, and insert it to the
delivery pipes [C]
Insert the joint pipe so that the step ...