I have a Craftsman 6.5hp eager1 push mower. It wasn't running so I took the carb apart cleaned it really well. It started and ran fine. I turned it off took off the blade, sharpened it. I put the blade back on and started the mower again and started mowing my lawn. I made one pass and it started rattling really bad. I shut it down and found I had not tightened the blade well enough. I tightened it down really well. I then tried to start it again but it will not. I get kickback when I pull the cord and sometimes it kinda backfires and white smoke will come out of the breather. I'm lost now please help.. I would say maybe the key was sheared but I didn't hit anything...