This is a quick video to show how a Briggs engine runs when the flywheel key breaks after the engine is stopped suddenly after hitting a solid object. The flywheel kept rotating for about 45 degrees. The repair is cheap and easy. Remove the flywheel and replace the key. To repair the broken flywheel key, first remove the flywheel retaining nut. You will need to stop the crank from turning when loosening the nut. I used a piece of timber between the blade disk and the body. Replace the nut to protect the thread (in case you miss with the hammer) and get a lever under the fly wheel and apply some upwards pressure. Give the top of the crank shaft a sharp crack with a hammer and the flywheel should release. Remove the broken flywheel key and replace the flywheel. Insert a new flywheel key, replace the nut and tighten. Replace the engine cover and starter and the job is done.