[wilkin250r]

It might be as simple as corroded wires and/or connection.

The fuel gauge is basically a resistance meter, and the sending unit is a resistance. The guage is expecting zero ohms on an empty tank, but a corroded wire or connection could easily introduce several ohms of resistance to the circuit.

To test the gauge, take the wire off the sending unit (a tan wire, I believe) and connect it to a good, clean frame ground. This should send your gauge to dead empty. If it still shows 1/4 tank, than you know the problem is with your gauge or wiring. If it DOES go to empty, then the problem is with your sending unit.