I'm not sure about the carb you are running, but if it doesn't have a float and shut off needle, the top of the tank when full should be about 1/8" to 1/4" below the fuel outlet in the carburetor, otherwise it will flood itself as it runs and run rough. There is enough venturi effect in these small carburetors to lift the gasoline from the tank up to the carb, as long as it doesn't have to lift it too far.---Brian