Your engine is a Tecumseh H30. This manual may help you. I would completely rebuild the carb with kit #631893. Before reassembling I would either give it a 24 hour soak in carb cleaner or take it to a shop and have it ultrasonicly cleaned.
http://www.mymowerparts.com/pdf/Tec...P-4-CYCLE-L-HEAD-FLAT-HEAD-ENGINES-692509.pdf
http://www.mymowerparts.com/pdf/Tec...P-4-CYCLE-L-HEAD-FLAT-HEAD-ENGINES-692509.pdf