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

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Charging Condition Inspection
Battery charging condition can be checked by measuring
battery terminal voltage with a digital voltmeter [A].
Remove the seat (see Seat Removal in the Frame chapter).
Disconnect the battery terminals.
NOTICE
Be sure to disconnect the negative (–) cable first.
Measure the battery ...
Thermostat Removal
Remove:
Fuel Tank (see Fuel Tank Removal in the Fuel System
(DFI) chapter)
Air Cleaner Housing (see Air Cleaner Housing Removal
in the Fuel System (DFI) chapter)
Throttle Body Assy (see Throttle Body Assy Removal in
the Fuel System (DFI) chapter)
Throttle Body Assy Holder Clamp [A]
...
Starter Motor Assembly
Install the positive brush assy [A] and the starter motor
terminal [B] as shown in the figure.
Replace the O-ring [C] with a new one, and install it.
Install:
Brush Springs [A]
Negative Brush Assy [B]
Turn the stopper side [C] to inside.
Tighten:
Torque - Brush Holder S ...