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 InspectionCamshaft, Camshaft Cap Wear Inspection
Remove the camshaft caps (see Camshaft Removal).
Cut the strips of plastigage (press gauge) to journal width.
Place a strip on each journal parallel to the camshaft installed
in the correct position.
Tighten the camshaft cap bolts and upper camshaft chain
guide bolts to the specified ...
Air Intake Duct Removal
Remove:
Upper Fairing Assembly (see Upper Fairing Assembly
Removal in the Frame chapter)
Meter Bracket (see Meter Unit Removal/Installation in
the Electrical System chapter)
Immobilizer Amplifier [A] (Equipped Models) (see Immobilizer
System Parts Replacement in the Electrical System
...
Caliper Installation
Install the caliper and brake hose lower end.
For the front caliper, be sure to install the collars [A].
Replace the washers on each side of hose fitting with new
ones.
Touch the brake hoses [A] to the stopper [B] of the caliper.
Front Calipers [C]
Rear Caliper [D]
Tighten:
To ...