The fuel bowl on the bottom of the carb, where the float is, although some systems have a glass bowl assemble next to the fuel outlet and may have a fuel shutoff. . . Is your gas tank higher than the carb? Some have a separate shut off valve in line? Is there a chunk of rust over the fuel outlet on the tank. Some of the tanks have a riser in the tank with a mesh filter on it. Look inside with a flashlight and check the condition of the tank.
The solenoid I am referring to is located on the bottom of the bowl, and when you unscrew it the bowl comes off, water and fuel will also come out You have a solenoid, or a nut that holds the bowl on the carb. You may have to take off the carb and unscrew the main jet and clean it out with a small wire. After you replace the filter, and hook up all the hoses, take off the plug wires, and with the bowl still off, and the float hanging down, turn the starter over for about 20 sec. If the fuel pump is working, you will see fuel coming out of the needle valve area. Push up on the float and see if the fuel stops. If all this is good, and you have cleaned the main jet, pinch off the fuel line, and replace the fuel bowl, then un pinch the fuel line.. Then put the plug wires back on, and try to start, with choke on, and when it starts to run, push the choke in part way. After it is running good, push the choke all the way in. I am not saying that what I have said will fix your problem, but I have done these things many many times, over 16 years. My first thoughts if an engine will not start, is to check for water in the gas, then spark.