Yes keep the mixture on the rich side to keep the engine temp's down and avoid engine damage (and keep run times to less than a minute or so). When it's really rich it makes the 4-stroking sound which is a lower pitch sound. It also sounds like the engine is missing explosions in the cylinder (because it is). Listen for this sound and you know you are in the rich region. Don't go too far from this sound on the needles to stay near the rich region. It should start to 2-stroke when it enters the lean region of operation (2-stroke operation is a higher pitch sound that does not sound like it's missing explosions in the cylinder). Good luck with tuning.