I have a Troy Bilt TB110 push mower that is running rough (about 1 year old). I picked it up from a friend because he couldn't get it started. I was able to clean up the carburetor and get it running, but it still surges a bit. When it surges, it shoots out a decent amount of black smoke. I ran some Sea Foam in it and it did not seem to make a difference. The air filter isn't new, but in very good shape. I am thinking that it is running rich. I pulled the spark plug and cleaned it up with a wire brush. The plug had a good amount of black carbon build up that was easy to remove with a paper towel. This model has the all plastic carburetor that does not have a float/needle in it. Any ideas or suggestions? I am stuck. Thanks for the help!!