Engine idles and responds to adjustment screw but at full throttle if I can get its rpms to full throttle it seems to be starving for fuel. I took the carb off and cleaned it with carb cleaner and blew it out with shop air. Still the same. Adjustment screw seems to do nothing. Is there a timing issue maybe? It ran fine last week but now it is just a problem. Could it be spark? Im pulling my hair out with this thing. Thanks in advance.