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 DiscFront Master Cylinder Installation
Apply silicone grease to the sliding surface of the brake
lever pivot bolt.
Tighten:
Torque - Brake Lever Pivot Bolt: 1.2 N·m (0.12 kgf·m, 11
in·lb)
Brake Lever Pivot Bolt Nut: 5.9 N·m (0.60 kgf·m,
52 in·lb)
Assemble the reservoir [A] and the bracket [B] as shown
in the figu ...
Air Cleaner
A clogged air cleaner restricts the engine’s
air intake, increasing fuel consumption,
reducing engine power, and
causing spark plug fouling.
This motorcycle’s air cleaner element
consists of a wet paper filter, which cannot
be cleaned.
The air cleaner element must be replaced
in acco ...
Cylinder Head Cover Installation
Replace the cylinder head cover gasket [A] with a new
one
Using a high flash-point solvent, clean off any oil or dirt
that may be on the silicone sealant coating area. Dry
them with a clean cloth.
Apply silicone sealant [B] to the cylinder head as shown
in the figure.
Sealant - Li ...