If the display function does not work, replace the meter unit.

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Exploded View
11. ZX1000JD/KD
AD: Apply adhesive.
AL: Tighten the two clamp bolts alternately two times to ensure even tightening
torque.
G: Apply grease.
L: Apply a non-permanent locking agent.
Specifications
...
Rear Master Cylinder Removal
Unscrew the brake hose banjo bolt [A] and remove the
brake hose (see Brake Hose and Pipe Replacement in
the Periodic Maintenance chapter).
Remove:
Rear Master Cylinder Mounting Bolts [B]
Foot Guard [C]
Screw and Stopper [D]
Bolt [E]
Front Footpeg Bracket Bolts [F]
Cable Guide [G ...
Parts Removal/Installation
WARNINGGasoline is extremely flammable and can be
explosive
under certain conditions. Turn the ignition
switch OFF. Do not smoke. Make sure the area is
well-ventilated and free from any source of flame
or sparks; this includes any appliance with a pilot
light.
NOTICE
...