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 Warp Inspection
Raise the rear wheel off the ground with the stand so that
it will turn freely.
Set a dial gauge [A] against the rear sprocket [B] near the
teeth as shown in the figure, and rotate [C] the rear wheel
to measure the sprocket runout (warp). The difference
between the highest and lowest di ...
Cylinder Head Removal
Remove:
Thermostat Housing (see Thermostat Removal in the
Cooling System chapter)
Exhaust Pipe (see Exhaust Pipe Removal)
Camshafts (see Camshaft Removal)
Heat Insulation Plate [A] (see Engine Removal in the
Engine Removal/Installation chapter)
Place a container under the coolant dr ...
Water Pump Impeller Disassembly/Assembly
Remove the water pump impeller (see Oil Pump Removal
in the Engine Lubrication System chapter).
The sealing seat and rubber seal may be removed easily
by hand.
Apply coolant around the surfaces of the rubber seal and
sealing seat.
Install the rubber seal [A] and sealing seat [B] into ...