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 InspectionKIBS Hydraulic Unit Installation
NOTICE
Brake fluid quickly ruins painted plastic surfaces;
any spilled fluid should be completely washed away
immediately.
Install the KIBS hydraulic unit together with the bracket.
Before installing the brake pipe, check to see that there is
no damage on the threads of the brake pipe joi ...
Starter Motor Assembly
Install the positive brush assy [A] and the starter motor
terminal [B] as shown in the figure.
Replace the O-ring [C] with a new one, and install it.
Install:
Brush Springs [A]
Negative Brush Assy [B]
Turn the stopper side [C] to inside.
Tighten:
Torque - Brush Holder S ...
Multifunction Meter
A. Multifunction Display
Odometer
Trip Meters
Current Mileage
Average Mileage
Fuel consumption
Stop Watch
B. Speedometer
C. Gear Position Indicator
D. Power Mode Indicator
E. S-KTRC Mode Indicator
F. Warning Symbols
G. Lap Counter/Coolant /
Intake Air Temperature
Meter
...