I have a 62cc Stihl engine with a side mounted carb on my 29% Extra. There isn't room in the cowl for a velocity stack on the carb. While test running it, I couldn't get the carb to go rich enough. I had noticed this tendency of this particular engine on the test stand. But if I put my hand in front of the carb, it would go rich. The air stream blowing by the carb inlet was causing it to go lean. I figured that it would not be a problem with the cowl on. However, there was enough airflow going through the cowl that I had the same problem with the cowl on; couldn't get the carb to go rich enough. Finally I made an air dam out of balsa, and glued it into the cowl in front of the carb. Problem solved.

AV8TOR