Several times we have been asked by various 'fresh' classic owners why the fuel gauge of their newly acquired beauty does not indicate the correct stock.
'Empty' often means that the tank is still at least a quarter full, when the fuel is filled to the brim, the meter indicates slightly more than 'half full'. The problem is most likely in the float-with-transmitter in the tank. It is not properly adjusted. Or readjust or replace. Meter problems rarely or never occur.