Had a buddy send me this email...anyone on here think they have a clue?? The mower is craftsman. The engine is briggs and stratton 125k02-0477 I used the mower once this season. Then I changed the blade.I think I did not tighten it enough. The next time I started the mower it started vibrating and then I have had a problem ever since. I have replaced the spark plug and the blade adapter as well. Also, the blade adapter shears quickly. If you guys have any clue...let me know!!?