Have B&S Sprint 3.75 hp mower, I cannot pull the starter rope. It acts as if something is binding inside engine. Blade can be turned by hand(with spark plug out, of course,) so I don't believe engine is siezed. At first thought safety switch was rubbing against flywheel, but that is not the trouble. Pull-cord works okay when not mounted. Engine was overheating before it quit, oil level was okay. I changed the oil and it still overheated but was running. I turned it off, let it sit over night and could not start it. Has anyone had same thing happen? Shaft does not appear visibly bent? How do I confirm that it is or is not the problem ? Thanks.