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 InspectionCable Removal
Remove:
Air Cleaner Housing (see Air Cleaner Housing Removal
in the Fuel System (DFI) chapter)
Right Lower Fairing (see Lower Fairing Removal in the
Frame chapter)
Loosen the nuts [A], and slide the lower end of the clutch
cable to give the cable plenty of play.
Screw in the ...
Caliper Fluid Seal Damage
The fluid seal (piston seal) [A] is placed around the piston
to maintain clearance between the pad and the disc. If
the seal is in a poor condition, it could lead the pad to wear
excessively or the brake to drag, which may cause the temperature
of the discs or the brake fluid to increase.
Re ...
Brakes
Brake Wear Inspection
Inspect the brakes for wear. For each
front and rear disc brake caliper, if the
thickness of either pad is less than
1 mm (0.04 in.), replace both pads
in the caliper as a set. Pad replacement
should be done by an authorized
Kawasaki dealer.
A. Lining Thickness
B. ...