1994 vmax fuel gauge not working

I have a 1994 yamaha Vmax 500, and the fuel gauge does not work. When the sled is off, the gauge reads Empty, then when I start the sled, it reads Full, at all times, no matter how much gas is in the tank. I'm not sure if its the sending unit thats bad, or the gauge or what, if anyone knows how to test any of these or know where to look, that'd be great.
Thanks
Jamie

Sounds like your sending unit is shorted out. Try this ~ drive 100 miles and get gas ! Its a 500 and it really likes gas ! Am I wrong ? For real ~ Unplug the wires going to the gage and test them to see if the gage is not messed up. If not, then the sending unit is faulty. Sometimes the wires get chafed and short out. Look for rubbed wires too. Good Luck !

alright man,
thanks a lot for the help
I got a schematic for the wiring today and know which wires go where.
Theres a green/black wire that goes straight from the sending unit to the gauge, im guessing this is the signal wire. Then theres a brown(I think power??) and black(ground) coming off the gauge, and a black(ground) off the sending unit.

So I guess I'll have to start ripping apart the sled to trace these wires, before I do that tho, i think im gonna hook an ohm meter up to a ground, and the green/black wire, wherever I can access it easily, and try moving the float arm up and down to see if the resistance changes, if it does, atleast i know its not bad.
if anyone else has some tips for me, let me know
thanks

alright, I have a little update now

I tested all the wires, and they're all fine.
I also found out, that with the sled running, it reads full all the time, but if I use a clothes hanger to push down on the float, the gauge will move down, so I know that somehow the float is not moving down, either its stuck on something, or theres not enough weight on it to pull it down(what I'm guessing).

so I guess im gonna have to pull everything apart so I can pull the sending unit out of the tank but I'll wait till summer to do that, dont wanna miss out on any sledding