Flip your seat forward, remove the wire off the sending unit, turn the key on and then ground that wire and see if the gauge moves. If it does get a new sending unit. Somewhere in the mid 60's they changed the ohm's rating on the sending unit I think it is 66, yours should be a 30 ohm and the later will be a 60 ohm. Someone may have already changed it and got the wrong one, look the screw heads over real goodand see if you can tell if they have been removed. Check with Tony at 4-5-6 he might have what you need. Also check if the tank is grounded,
