Pull the bowl off the carb and remove the float and needle valve. Try to blow air into the gas line again. If air still won't pass remove the needle valve seat from the carb body and let everything sit in carb cleaner overnight to soften things up. Then try to blow air again. The higher the pressure the better. I had to do this on an old motorcycle carb that I think a spider or other insect got into and made a little plug. Took some time, but it came out. I think I had to use a wire as well to poke it out.
Anyone know of a new project machine for me around Wisconsin?