Since it will spin with the plug out, but not in, to me, it would seem it would take gas in, but on cumbustion/exhaust, there is a blockage.
Had it with a vehicle, ran like crap, no power. Finally they cut the muffler and it was packed full by mice storing food, so think yours may be plugged with derbies or something.
Min is going on 15 years and still going strong. June 24 2003 a tornado went through my place, had to have a little work done on it and still going good. I think it need a carb and choke work.