I picked up a Craftsman 4.5 hp 4 stroke lawnmower engine off the street yesterday, to hopefully put in a bike at some point. The problem is every time i pull the starter rope it backfires through the carburetor and spins the engine backwards, and it has already broken two starter ropes with the backwards spinning. The only thing i can think of that could cause this would be over advanced spark timing, but that seems unlikely since the magnet that triggers the spark is on the flywheel, which is very well attached to the engine shaft. I suppose the flywheel could have slipped a little on the shaft. Anyway, what do you guys think is causing this?
