If the carburetor is the later model shown in AVB's illustration, the screw is supposed to be all the way in there and tightened. You need to remove that screw, clean the holes in it, and spray cleaner into the recess behind it, under pressure, to clean the drilling in the carburetor body. However I'm not clear on just what you have and haven't done. Did you remove the carburetor, clean the two filters, clean the main jet, and inspect and most likely replace the diaphragm? The carburetor is almost certainly still in need of attention, since it stopped running and needed choke to restart.