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 InspectionBreak-in
The first 1 600 km (1 000 mi) that the motorcycle is ridden is designated
as the
break-in period. If the motorcycle is not used carefully during this period, you
may
very well end up with a “broken down” instead of a “broken in” motorcycle after
a
few thousand kilometers.
The fol ...
Maintenance and adjustment
The maintenance and adjustments outlined in this chapter must be carried
out in
accordance with the Periodic Maintenance Chart to keep the motorcycle in good
running condition. The initial maintenance is vitally important and must not be
neglected.
With a basic knowledge of mechanics and the ...
Commutator Cleaning and Inspection
Clean the metallic debris off the between commutator
segments [A].
NOTE
Do not use emery or sand paper on the commutator.
Check the commutator for damage or abnormal wear.
Replace the starter motor with a new one if there is any
damage or wear.
Visually inspect the commutato ...