Fuel gauge

had that happen on my 75 scamp i drove for a while.
we still had one of the old gage testers here.check with some local shops maybe someone still has one.
you hook it up at tank and adjust dial and watch gage.mine worked fine.
pulled sender to put a new float and sock on it anyway.
resistance checked good.
was bad ground.soldered a piece of 10-12 ga wire to feed pipe and bolted other end to body.worked like a charm