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 InspectionPiston Ring End Gap Inspection
Place the piston ring [A] inside the cylinder (upper
crankcase), using the piston to locate the ring squarely
in place. Set it close to the bottom of the cylinder, where
cylinder wear is low.
Measure the gap [B] between the ends of the ring with a
thickness gauge.
Piston Ring End Gap ...
Meter Unit Circuit (ZX1000K Model)
1. Ignition Switch
2. Joint Connector F
3. Stop Watch Button
4. Oil Pressure Switch
5. Crankshaft Sensor
6. Water Temperature Sensor
7. Gear Position Switch
8. Intake Air Temperature Sensor
9. ESD ECU (ZX1000JD/KD)
10. ECU
11. Rear Wheel Rotation Sensor
12. Frame Ground 1
13. Engine ...
Rear Sprocket Removal
Remove the rear wheel (see Rear Wheel Removal in the
Wheels/Tires chapter).
NOTICE
Do not lay the wheel on the ground with the disc
facing down. This can damage or warp the disc.
Place blocks under the wheel so that the disc does
not touch the ground.
Remove:
Rear Sprocket Nu ...