I was mowing the lawn the other day and hit a stump. Mower immediately shut off and would not restart. When you pull the cord, the engine does not start. It seems like when I pull the cord the engine only turns over one revolution. I replaced the flywheel key since it was pretty much sheered off. I thought that would fix the problem, but appearantly not. Also after replacing the flywheel key, I was pulling the cord checking things out and it yanked back and almost took my hand off. Any suggestions?