Time for all new fuel lines, hoses, hose clams and maybe a new fuel pump.

I suppose the fuel could evaporate from the carb, it has air bleeds that could allow evaporation, (the bowl vent has a hose going to the carbon canister to collect the fumes, right?) The fuel has to be draining back through the pump to make the line between the pump and carb empty. Otherwise it shouldn't take very long for a good fuel pump to refill the carb, unless there was no fuel at the pump. I don't see the fuel flowing back up into the tank, which is often higher then the line. (The fuel line is higher then the tank where it run above the rear axle before dropping down to the frame rails) The section of fuel line above the axle should stop and fuel from returning into the tank between it and the pump. If the fuel can't return to the tank, the fuel line, hoses, or hose clamps must be leaking, or the pump is leaking fuel, or is too weak to move the fuel like it should, otherwise where did the fuel go? Gene