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 InspectionHandlebar Removal
Remove:
Steering Damper (see Steering Damper Removal)
Clutch Lever Clamp Bolts [A]
Clutch Lever Assembly [B]
Left Switch Housing [C]
Handlebar Weight [D]
Left Handlebar Grip [E]
Remove:
Front Master Cylinder [A] (see Front Master Cylinder Removal
in the Brakes chapter)
...
Headlight Bulb Replacement
Turn the cover [A] counterclockwise, and remove it.
Disconnect the headlight connector [A].
Open the clamp [B], and remove the bulb.
NOTICE
When handling the quartz-halogen bulb, never
touch the glass portion with bare hands. Always
use a clean cloth. Oil contamination from hand ...
Oil 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 ...