Replace it if necessary.

Inner Tube Inspection
Spring Tension InspectionMaster Cylinder Inspection (Visual Inspection)
Remove the master cylinders (see Front/Rear Master
Cylinder Removal).
Disassemble the front and rear master cylinders (see
Master Cylinder Rubber Parts Replacement in the Periodic
Maintenance chapter).
Check that there are no scratches, rust or pitting on the
inner wall [A] of each ma ...
Lower Fairing Removal
Remove the quick rivets [A].
Remove:
Quick Rivets [A]
Bolts [B]
Pull up the core by the flat-head screwdriver (–), and then
remove the quick rivet.
Clear the hook portions on the upper edges [C] from the
slots, and remove the left lower fairing [D].
While pulling down ...
Rear Brake Pad Installation
Check that the pad spring is in place on the caliper.
Push the caliper piston in as far as it will go.
Install the piston side pad [A] first, and then another pad.
Fit the brake pad end into the recess [B] of the caliper
holder.
Install the pad pin and the plug.
Tighten:
Torque - ...