Have you checked to make sure that your fuel switch is not leaking? If you are sure that and the hoses are fine then it has to be the carb fuel overflow. There should be a hose attached to the bottom of the carb bowl. That is the carb overflow. THe hose keeps the fuel from hitting the engine, although the carb shouldn't overflow like you say it is. Either the float is stuck, mis-adjusted, or is broken. Pop the bowl off the carb, remove the float and check it for cracks. If it looks alright and upon re-installation the carb still overflows, you will need to adjust the fuel height by bending the float tang. Instructions are in the service manual, or we can help you out with that. Send me a PM if you need more detailed instructions.
Anyone know of a new project machine for me around Wisconsin?