Hi Roadtec,

You could try this you will need a zappi hand set pluged into the power controller.

Press enter to open main menu.
The first item on the list appears
Using the roll up roll down keys to scroll the list select program VACC
The program VACC appears press enter.
The current maximumum values for forward and reverse appear press enter.
The chopper is now ready to record max and min potentiometer signals for forward and reverse.
Turn the throttle lever in both directions take care to move the lever slowly to the end of its stroke or travel.
The new min and max values in the respective directions appear on the display. The arrow shows the select direction. Press out. You will be asked to confirm the new values press enter and then out.
This is very old info and I can not gar ranted it will work.
Regards Nero