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 DiscEvaporative Emission Control System Inspection (CAL and SEA-B1 Models)
Inspect the canister as follows.
Remove the upper fairing assembly (see Upper Fairing
Assembly Removal in the Frame chapter).
Remove the canister [A].
Visually inspect the canister for cracks or other damage.
If the canister has any cracks or bad damage, replace it
with a new one.
NO ...
Oil Pressure Relief Valve Inspection
Remove the oil pressure relief valve (see Oil Pressure
Relief Valve Removal).
Check to see if the valve [A] slides smoothly when pushing
it in with a wooden or other soft rod, and see if it comes
back to its seat by spring [B] pressure.
NOTE
Inspect the valve in its assembled stat ...
Windshield and Other Plastic Parts
After washing use a soft cloth to
gently dry plastic parts. When dry,
treat the windshield, headlight lens,
and other nonpainted plastic parts with
an approved plastic cleaner/polisher
product.
NOTICE
Plastic parts may deteriorate
and break if they come in contact
with chemical substances
...