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 DiscCoolant Deterioration Inspection
Remove the right lower fairing (see Lower Fairing Removal
in the Frame chapter).
Visually inspect the coolant in the reserve tank [A].
If whitish cotton-like wafts are observed, aluminum parts
in the cooling system are corroded. If the coolant is
brown, iron or steel parts are rusting. I ...
CAN Communication Line
CAN Communication Line
Resistance Inspection
In this model, resistors for CAN communication line are
built in the ECU [A] and meter unit.
Refer to the Meter Unit Inspection in the Electrical System
chapter for the resistor in the meter unit.
Turn the ignition switch to OFF.
Remove:
EC ...
Stick Coil Inspection
Remove the stick coils (see Stick Coil Removal).
Measure the primary winding resistance [A] as follows.
Connect the hand tester between the coil terminals.
Set the tester to the × 1 Ω range, and read the tester.
Measure the secondary winding resistance [B] as follows.
Conn ...