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 DiscECU Communication Error (Service Code 39)
ECU Communication Line Inspection
When the data is not sent from the ECU to the meter unit
for more than about 10 seconds, the service code 39 is
displayed.
The data is sent through the CAN communication line.
The service code 39 is detected with the meter unit.
When the user mode, this commun ...
Coolant 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 ...
Special Tools
Bearing Driver Set:
57001-1129
Jack:
57001-1238
Bearing Remover Head, 25 × 28:
57001-1346
Bearing Remover Shaft, 13:
57001-1377
Jack Attachment:
57001-1608 ...