I have a 1984 8hp, manual start, and I can't get it to idle without pumping the choke. I can however, run it at high RPM with very minor sputtering. It seems to me that it's not getting enough fuel for some reason. I have taken apart the carb part way, sprayed out the high and low speed jets with carb cleaner, and cleaned everything I can. Upon re-installation, I still encounter the same problem. I am stumped! Any ideas about what to try next?