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 InspectionWiring Diagram (Other than US, CA and CAL without KIBS Models)
ZX1000JC
ZX1000JD
...
Front Master Cylinder Removal
Remove the reservoir mounting bolt and nut [A].
Unscrew the banjo bolt [A] and disconnect the brake hose
from the master cylinder (see Brake Hose and Pipe Replacement
in the Periodic Maintenance chapter).
Unscrew the clamp bolts [B], and take off themaster cylinder
as an assembl ...
Oil Pump Drive Gear Installation
Install is the reverse of removal. Note the following.
First, engage the oil pump chain [A] to the gears, and then
install the oil pump drive gear [B].
Turn the “OUT� mark [C] to outside.
Apply a non-permanent locking agent to the oil pump drive
chain guide bolt and the oil pump drive ...