If any is worn down to the service limit, replace the brush assy.
Starter Motor Brush Length [B] Standard: 12.05 mm (0.4744 in.) Service Limit: 6.55 mm (0.258 in.)

Starter Motor Assembly
Commutator Cleaning and InspectionOil Cooler Removal
Remove:
Coolant (Drain, see Coolant Change in the Periodic
Maintenance chapter)
Engine Oil (Drain, see Engine Oil Change in the Periodic
Maintenance chapter)
Lower Fairings (see Lower Fairing Removal in the Frame
chapter)
Water Hose Ends [A] (Disconnect)
Remove:
Oil Cool ...
Upper Fairing Assembly Disassembly
Remove:
Upper Fairing Assembly (see Upper Fairing Assembly
Removal)
Headlight (see Headlight Removal/Installation in the
Electrical System chapter)
City Light (LED) (see City Light (LED) Removal/Installation
in the Electrical System chapter)
Remove the screws [A], and separate each ...
Front Fork Oil Change
Remove the front fork (see Front Fork Removal (Each
Fork Leg)).
Turn the spring preload adjuster fully counterclockwise for
removing the piston rod assy easily.
Hold the inner tube lower end in a vise.
Using the wrench [A], unscrew the top plug [B] out of the
outer tube.
Special Too ...