If there are notches worn into the splines, replace the sub clutch hub. Also, replace the steel plates if their teeth are damaged.

Clutch Housing Finger Inspection
Damper Cam InspectionFront Forks/Rear Shock Absorber Operation Inspection
Pump the forks down and up [A] 4 or 5 times, and inspect
the smooth stroke.
If the forks do not smoothly or noise is found, inspect the
fork oil level or fork clamps (see Front Fork Oil Change in
the Suspension chapter).
Pump the rear seat down and up [A] 4 or 5 times, and
inspec ...
Wiring Diagram (Other than US, CA and CAL with KIBS Models)
ZX1000KC
ZX1000KD
...
Braking
Close the throttle completely, leaving
the clutch engaged (except when
shifting gears) so that the engine will
help slow down the motorcycle.
Shift down one gear at a time so that
you are in 1st gear when you come
to a complete stop.
When stopping, always apply both
brakes at the ...