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

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Exhaust Butterfly Valve Actuator Removal
NOTICE
Never drop the exhaust butterfly valve actuator especially
on a hard surface. Such a shock to the actuator
can damage it.
Remove:
Front Seat (see Front Seat Removal in the Frame chapter)
Clamp [A]
Screws [B] and Washers
Slide the covers [A] and loosen the lock nuts [B] ...
Piston Ring End Gap Inspection
Place the piston ring [A] inside the cylinder (upper
crankcase), using the piston to locate the ring squarely
in place. Set it close to the bottom of the cylinder, where
cylinder wear is low.
Measure the gap [B] between the ends of the ring with a
thickness gauge.
Piston Ring End Gap ...
Hoses and Pipes
Hose Installation
Install the hoses and pipes, being careful to follow bending
direction. Avoid sharp bending, kinking, flattening or
twisting.
Run the hoses (see Cable, Wire, and Hose Routing section
in the Appendix chapter).
Install the clamp [A] as near as possible to the hose end
...