Ok, just found another possible cause....Please let me know if this is a possiblity or not!! I was in the process of taking the packing out of the muffler and there is a long round pipe in the center (possibly the baffle?) well, this pipe not only had wasp nest forming inside of it but the ends were falling apart from rust! Could part of that falling apart have entered the cylinder head and made those marks on the top of the piston? Thanks for anyone's opinions...I am desperatly trying to figure this out!