it is on empty but the tank is full

 

check fuel sender plug underneath the back seat...plug and unplug and see if needle will move...otherwise your gauge is toast or in-tank level is bad.

 

sorry to thread jack, but mine has a full tank until about 80 miles, then it goes straight to 3/4, then another 50 miles and it says i have 1/4 tank left, doesnt make any sense, im not driving it hard either. could that just be a bad sender?
and how do u replace the sender?

 

It's a dealer part unless you want to get one from a junk yard...it's like replacing your fuel pump, you have to bring down the gas tank and replace the float mechanism.

 

u cant just pull the fuel pump out and do it with the gas tank in?

 

unfortunately, you can't... it's a real pita

 

thats what i thought, no reason to remove the gas tank