If the shaft is bent, straighten or replace it.
If the serration [B] are damaged, replace the shaft.
If the spring [C] is damaged in any way, replace it.
If the shift mechanism arm [D] is damaged in any way, replace the shaft.

If the ratchet [A], pawls [B], pins [C] or springs [D] are damaged in any way, replace them.

If it is loose, unscrew it, apply a non-permanent locking agent to the threads, and tighten it.
Torque - Shift Shaft Return Spring Pin: 29 N·m (3.0 kgf·m, 21 ft·lb)
If the lever or spring are damaged in any way, replace them.
If they are badly worn or if they show any damage, replace it.

External Shift Mechanism Installation
Wheels/TiresWiring Diagram (Other than US, CA and CAL without KIBS Models)
ZX1000JC
ZX1000JD
...
Cylinder Head Installation
NOTE
The camshaft cap is machined with the cylinder head,
so if a new cylinder head is installed, use the cap that
is supplied with the new head.
Install the dowel pins.
Replace the cylinder head gasket with a new one.
Replace the cylinder head bolt washers with new ones.
Apply molybden ...
Mode-switching
Depress the S-KTRC button on the left handlebar switch
to change the mode. The mode can be changed only when
the throttle grip is closed completely.
The S-KTRC OFF can be selected only when the motorcycle
is at a stop. Changing to mode 1 from S-KTRC OFF
is possible while riding.
NOTE
...