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 InspectionSeat Cover Installation
Installation is the reverse of removal. Note the following.
When installing the pad [A], install it along the corner [B]
as shown in the figure.
When installing the pad [C], align the ends [D], along the
corner [E], and wrap [F] the upper edge of the seat cover.
Install the damper [A] ...
Crankshaft Main Bearing
Insert/Journal Wear Inspection
Split the crankcase (see Crankcase Splitting).
Cut strips of plastigage to journal width.
Place a strip on each journal parallel to the crankshaft
installed in the correct position.
Tighten the crankcase bolts to the specified torque (see
Crankcase Assembly).
NOTE
Do not turn ...
Lower Crankcase Assembly
Install the ball bearing [A] and the oil level inspection window
[B] until they are bottomed
Apply soap and water solution to the oil level inspection
window before installation.
Install the new circlip [C].
Apply a non-permanent locking agent to the oil passage
plug [D].
Tighten: ...