Try reading this a few times and you to can become a YS expert. [link=http://home.comcast.net/~mark.fuess/ys110.htm]YS info[/link] Don't let other engine "gurus" at your field get near you or the engine while you are adjusting it. You MUST have a tach. Again, don't listen to expersts who stand there and say it's lean, it's rich, turn the regulator screw blah, blah ,blah.... They don't know whay they are talking about.