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 InspectionExploded View
AL: Tighten the two clamp bolts alternately two times to ensure even
tightening torque.
G: Apply grease.
R: Replacement Parts
G: Apply grease.
L: Apply a non-permanent locking agent.
R: Replacement Parts
Specifications
...
Brake Disc Installation
Install the brake disc on the wheel so that the marked side
[A] faces out.
Front Brake Discs [B]
Rear Brake Disc [C]
Apply a non-permanent locking agent to the threads of
the brake disc mounting bolts.
Tighten:
Torque - Brake Disc Mounting Bolts: 27 N·m (2.8 kgf·m, 20
...
Air Cleaner Housing Installation
For ZX1000JD/KD, be sure to install the pad [A].
Install the clamp bolt heads [A] inside as shown in the
figure.
Install the air cleaner housing on the throttle body assy.
Push in the ducts [B] touch the stoppers [C] of the throttle
body.
Be sure the hoses are routed correctly ...