Lawn mower bangs (up top) when it starts
Especially when the engine is cold. Also, sometimes it backfires, and a puff or two of blue smoke comes out of the left side. Sometimes the rope will pull back on me when I am pulling it. It's a bit scary to start. And I am very concerned about this banging; it bangs quite loudly for a few times only and then once up and running straightens out.