The last couple of "old" engines I rebuild had the wrist pin frozen in either the piston or the con rod. The only way I could get it freed up was to disassemble the engine to get to the wrist pin. Glad I did as the crankshaft would turn but the balls in the rear bearing were frozen to the outer race. The engine turned over nice but god forbid had I started the thing.

My recommendation is a complete disassembly, cleaning and replace the bearings along with any rubber parts that need replaced. IMO why cheap out on a nice engine and potentially ruin it. $30 spent now will pay in the end.

Ken