LIGHTLY thread it all the way in until it "touches" then back out one full turn...
once the motor is fully warmed up, slowly thread it in..listen to see if the rpms drop (or rise)...if/when they do STOP...now, slowly start backing it out, listen for when the rpms drop...when that happens STOP again, now set it right in the middle of then two...
basically...find where the highest RPM occurs..your gonna find that there is a small range of screw rotation where it does`nt "sound" to make a difference..you want to be right in the middle..if anything, error on the side of slightly rich to help with the "off the line bog" as they say..
when you do this, do it SLOWLY and give the motor time to respond...just start out at one full turn out...then pick a direction and take it, go each way until you have found the highest rpm position..then find out how far in and out you can go before the rpms begine to drop..set it right in the middle of that...hope that explination made sence..
just to add....while not a rule..it is typical for a manufacture to use a carb and pilot etc for a given motor, that will end up with the screw set somewhere between one full turn out, and three turns..which is NOT to say there`s an "issue" if you end up at a half a turn, but just thought I`d mention it..
I`ve ran across countless machines which ended up at 1/2-3/4 etc...not a biggy..but I would suggest starting out at one full turn...
