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

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Engine Sprocket Installation
Replace the sprocket washer and axle cotter pin.
Install the engine sprocket onto the output shaft.
Apply molybdenum disulfide oil solution to the threads
and seating surface of the engine sprocket nut.
Tighten:
Torque - Engine Sprocket Nut: 145 N·m (14.8 kgf·m, 107
ft·lb)
NOTE
...
Fuel Consumption
This display mode shows the fuel
consumption in Liter or Gallon by numerical
value counted from the start of
measuring to present time.
A. Fuel Consumption
B. “L”
While the fuel consumption is displayed,
push the lower button and
hold it in until the fuel consumption
values re ...
Relay Circuit Inspection
Remove the relay box (see Relay Box Removal).
Check conductivity of the following numbered terminals
by connecting the hand tester and one 12 V battery to the
relay box as shown in the figure (see Relay Box Internal
Circuit in this section).
If the tester does not read as specified, re ...