I recently purchased a Craftsman M250 160cc self-propelled mower from Lowes. The mower had worked great so far. Unfortunately, I recently ran over a piece of metal. The blade and engine both came to an immediate stop. I inspected the blade for damage and it appeared to look normal. When I rotated the blade, the bolt in the middle did not budge. I am relatively amateur to lawn care but that would indicate that there isn't severe damage to the crankshaft, correct? My mower has 6 height settings. For the sake of this post, I will refer to "1" as the lowest "6" as the highest. I had been using setting "3" to mow. When I started the mower back up after hitting the metal, it started fine so I don't believe there is any issue with the spark plug. It ran for a little while and was still cutting. However, it began to make an awful sound and then came to a stop. I moved the height up to 6 and then 5 and tested again. It would run normally on those settings and would cut taller grass as normal. It seemed to struggle when cutting grass on the lower setting and would then stop. What could the problem be here? It had been cutting grass at that height just fine before I hit the metal so I know it wasn't too low of a setting for that height of grass. I was thinking it isn't related to the spark plug, blade, fuel line, or engine considering that those aspects seemed to be unaffected on the higher settings. I also made sure the mower deck, blade, wheels, etc. were free of grass buildup.
Yep, this is what they do when you hit something with the blade and it stops the engine instantly, they have an Aluminum key that aligns the flywheel on the crank that shears. Sometimes that sudden hit / stop can also bend the crank where the blade bolts on! Make sure the bottom of the crank is not bent then, take the flywheel off, if the key is sheared, replace it.
