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.
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Crankshaft Side Clearance Inspection
Insert a thickness gauge [A] between the thrust washer
[B] on the crankcase and the crank web [C] at the #3 main
journal to determine clearance.
If the clearance exceeds the service limit, replace the
thrust washers as a set and check the width of the crankshaft
#3 main journal.
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Mode-switching
Depress the S-KTRC button on the left handlebar switch
to change the mode. The mode can be changed only when
the throttle grip is closed completely.
The S-KTRC OFF can be selected only when the motorcycle
is at a stop. Changing to mode 1 from S-KTRC OFF
is possible while riding.
NOTE
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