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

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Subthrottle Sensor Output Voltage Inspection
Measure the output voltage at the subthrottle sensor in
the same way as input voltage inspection, note the following.
Disconnect the subthrottle sensor connector and connect
the setting adapter [A] between these connectors.
Special Tool - Throttle Sensor Setting Adapter: 57001
-1538
...
Alternator Rotor Installation
Using a cleaning fluid, clean off any oil or dirt on the following
portions and dry them with a clean cloth.
Crankshaft Tapered Portion [A]
Alternator Rotor Tapered Portion [B]
Install the alternator rotor.
Using a cleaning fluid, clean off any oil or dirt on the
washer [A] ...
Meter Unit Circuit (ZX1000J Model)
1. Ignition Switch
2. Joint Connector F
3. Stop Watch Button
4. Oil Pressure Switch
5. Crankshaft Sensor
6. Water Temperature Sensor
7. Gear Position Switch
8. Intake Air Temperature Sensor
9. ESD ECU (ZX1000JD/KD)
10. ECU
11. Rear Wheel Rotation Sensor
12. Engine Ground
13. Battery ...