I have a 8 year old (approximately) 6.5 hp self propelled Craftsman mower that "kicks back" violently when I try to crank it. I hit a stump with it a month ago and bent the blade very bad! I replaced the blade and saw no evidence of shaft problems as the mower cranked and mowed as before. any suggestions? The upper frame is rusted through in a space about the size of a golf ball. Should I just I purchase a replacement or try to get this one through the summer?