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 DiscOil Level Inspection
If the oil has just been changed, start
the engine and run it for severalminutes
at idle speed. This fills the oil
filter with oil. Stop the engine, then
wait several minutes until the oil settles.
NOTICE
Racing the engine before the oil
reaches every part can cause engine
seizure.
...
Overview
S-KTRC is a highly sophisticated system based on MotoGP racing technology.
Unlike the KTRC
system used on the GTR1400 ABS (Concours 14 ABS in N. America), which is
designed to offer rider
reassurance when traversing slippery surfaces, S-KTRC, is designed to maximize
forward motion,
allowing ...
Washing Your Motorcycle
Rinse your bike with cold water from
a garden hose to remove any loose
dirt.
Mix a mild neutral detergent (designed
for motorcycles or automobiles)
and water in a bucket. Use
a soft cloth or sponge to wash your
motorcycle. If needed, use a mild degreaser
to remove any oil or greas ...