No problem, none taken because I misunderstood what you meant by bad and there are so many stories around saying that running rich will damage an engine (ABC type anyway). I fully agree that being shown how to tune an engine is worth more than any amount of words.

But to try to help out the OP, it seems that the engine is running a bit rich at idle (puttering and not sounding smooth) but too lean at full throttle (revs a bit then dies). The "little knob on the side of the engine" I can only assume you mean the high speed needle valve which controls the mixture at full throttle. Wind it out a turn and try going slowly to full throttle again. If it still just dies then open it some more. Most engines will run on the rich side at 2-3 turns open.