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 InspectionTie-Rod and Rocker Arm Bearing Removal
Remove:
Tie-Rod (see Tie-Rod Removal)
Rocker Arms (see Rocker Arm Removal)
Swingarm (see Swingarm Removal)
Sleeves [A]
Oil Seals [B]
Remove the needle bearings [C], using the bearing remover
head and bearing remover shaft.
Special Tools - Bearing Remover Head,
15 ×
17: ...
Check 3-5: Warning Indicator Light (Red LED) (Oil Pressure Warning)
Inspection
Connect the leads in the same circuit as Check 3-2.
Connect the terminal [10] to the battery (–) terminal.
Check that the oil pressure warning symbol [A] and the
warning indicator light (Red LED) [B] go on.
If the indicator light does not go on, replace the meter unit.
...
Battery Maintenance
It is the owner’s responsibility to keep
the battery fully charged. Failure to do
so can lead to battery failure and leave
you stranded.
If you are riding your vehicle infrequently,
inspect the battery voltage
weekly using a voltmeter. If it drops
below 12.8 volts, the battery should be
...