it's most likely your jet key, on your carb there will be a flat head screw, I'd take a pic of mine but they are all in storage for the winter. but if you pull that out and see a ring around the end that means it has been screwed in to far and it's messing up the fuel flow. Also the timing may be off, when these motors are built the timing is advanced a hair so the key won't fit back in, it's just torqued down heavily.