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 InspectionFuel Pump Removal
WARNINGGasoline is extremely flammable and can be
explosive
under certain conditions, creating the
potential for serious burns. Make sure the area is
well-ventilated and free from any source of flame
or sparks; this includes any appliance with a pilot
light. Do not smoke. T ...
Cooling System Flushing
Over a period of time, the cooling system accumulates
rust, scale, and lime in the water jacket and radiator. When
this accumulation is suspected or observed, flush the cooling
system. If this accumulation is not removed, it will clog
up the water passage and considerable reduce the efficiency
...
Valve Clearance
Valve and valve seat wear decreases
valve clearance, upsetting valve timing.
NOTICE
If valve clearance is left unadjusted,
wear will eventually
cause the valves to remain
partly open; which lowers performance,
burns the valves and
valve seats, and may cause serious
engine damage.
Valve cle ...