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 DiscTire Repair
Currently two types of repair for tubeless tires have come
into wide use. One type is called a temporary (external) repair
which can be carried out without removing the tire from
the rim, and the other type is called permanent (internal)
repair which requires tire removal. It is generally unders ...
Air Intake Duct Assembly (Other than US, CA and CAL Models)
Install the seals [A] as shown in the figure.
Fit the projections [A] of the air intake valve to the hole [B]
of the air intake ducts.
Tighten:
Torque - Air Intake Duct Assembly Screws: 1.5 N·m (0.15
kgf·m, 13 in·lb)
Hang the shaft [A] to the air intake valve securely ...
Subthrottle Sensor Output Voltage Inspection
Measure the output voltage at the subthrottle sensor in
the same way as input voltage inspection, note the following.
Disconnect the subthrottle sensor connector and connect
the setting adapter [A] between these connectors.
Special Tool - Throttle Sensor Setting Adapter: 57001
-1538
...