fuel guage

[BarryQ]

I have a 1978 XS 1100, When I turn on the ignition on the fuel guage goes past full, Shut it off and the guage goes back to empty, The tank is about 1/2 full. Any thoughts on this If it might be the guage or the sending unit??

[skids]

Sorry, but I forgot to check to see which model you have before posting, but:

For the standards, you can test the supply voltage with the clip to the sender disconnected. I don't have the manual handy but it is I think 7 volts.

You can test the sending unit ohms (tank empty) on the other side of the clip. Again, I dont have the specs, but you check it with the tank empty, then you rotate the tank to raise the float to maximum and check it again. I suppose it makes more sense to NOT take off the tank, check it empty and then fill it up to check it again, but I always do it the hard way 'cause that is how I am

If everything checks out OK with the sender and the supply voltage, you probably have a bad bimetallic tang that heats and deflects the gage needle. They break at the base. If that is the case, I have not been successful at fixing that...

[3Phase]

Barry, remove the fuel tank and check to see if the Green wire that runs from the fuel gauge down to the fuel tank sender is pinched against the frame or the tank and shorted to ground.

If that's okay, make sure the Green wire is not shorted to ground in the headlight bucket or anywhere else along the frame.

You can test the fuel tank sender with an Ohm meter to see if its shorted:

Full = 6 to 10 Ohms
Half = 28.5 to 36.5 Ohms
Empty = 75 to 85 Ohms

[BarryQ]

fuel gauge

I want to say thanks for the helpful answers .This is a great place