It is bigger than what I am used to, but if it is ABC it is likely OK. I would take the backplate off and see why is is rattling. Maybe just the rod rattling. If it is ringed or lapped steel, it may have got a bit too hot. More oil added may help to seal it better if it is loose or warped. Maybe 25% oil like the old worn out Foxes like. I'll be watching this thread because I have a .28 Thunder Tiger Prothat overheats like that too. I always thought overpropping a motor made it overheat. Either way Iwould run it on the rich side for a while.