I personally think it would be cheaper to just purchase another complete unit from Harbor Freight than to purchase an engine and go thru the swap. BUT, once you've taken the cover off the end of the generator head, there's a thru-bolt that goes thru the generator into the crankshaft of the engine. It's a tapered fit and hard to brake free, but that's what needs to be done. After turning the thru-bolt out one turn, and the case id unbolted from the engine case, smack it once with a hammer on the head of thru-bolt. Hopefully that will free the taper from the crankshaft because all is freed and the armature taper is all that holds it.