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 DiscFuel Filter Cleaning
The fuel filter [A] is built into the fuel pump and can not be
cleaned or checked.
If the fuel filter is suspected of clogging or being damaged,
replace it with the fuel pump as a set.
Fuel Pump Circuit
1. Ignition Switch
2. Engine Stop Switch
3. Joint Connector E
4. ECU
5. Engine G ...
Check 3-6: Neutral Indicator Light (LED) Inspection
Connect the leads in the same circuit as Check 3-2.
Connect the terminal [8] to the battery (–) terminal.
Check that the neutral indicator light (LED) [A] goes on.
If the indicator light does not go on, replace the meter unit.
...
Storage of Removed Parts
After all the parts including subassembly parts have been
cleaned, store the parts in a clean area. Put a clean cloth
or plastic sheet over the parts to protect from any foreign
materials that may collect before re-assembly.
Inspection
Reuse of worn or damaged parts may lead to serious acci ...