When it starts, it smokes a lot. The gas mix is correct. It is hard to start and needs to have the choke continually adjusted to keep running.

Hi,
Sounds like a double-whammy in that it sounds like you have a carb not working up to par and a clogged muffler screen. Additional info would be that if you see a lot of oily residue on the body, the cylinder has come loose from the crankcase.
Peace,
Clarke