You can check the fuel lines in the tank for splits and holes. Do you have an electric starter? Spin it faster and see if fuel comes up the line. Or plug the exhaust port when you flip it a few times. Have you changed the location of your engine or feul tank. If your tank is to low in relation the the carburetor spray bar gravity might be your culpret. (spray bar is idealy center with the tank (you rarely get an ideal set up))