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 InspectionIntake Air Temperature Sensor Output Voltage Inspection
NOTE
Be sure the battery is fully charged.
Turn the ignition switch to OFF.
Remove the fuel tank (see Fuel Tank Removal in the Fuel
System (DFI) chapter).
Disconnect the intake air temperature sensor connector
and connect the measuring adapter [A] between these
connectors as shown in ...
Front Wheel Rotation Sensor Signal Abnormal (Service Code b 42)
Measure the air gap between the front wheel rotation sensor
and sensor rotor.
Thickness Gauge [A]
Air Gap
Standard: 0.4 1.6 mm (0.02
0.06 in.)
If the measurement is not the standard, check each part
for deformation and looseness and correct accordingly.
If the measurement is t ...
Stem, Stem Bearing Installation
Replace the bearing outer races with new ones.
Drive them into the head pipe at the same time.
Special Tools - Head Pipe Outer Race Press Shaft [A]:
57001-1075
Head Pipe Outer Race Driver,
55 [B]: 57001
-1446 or Bearing Driver Set: 57001-1129
Apply grease to the outer races.
...