Al I will have to give you this one. Dead on!I've never race 4 cycles, but when I was racing 2 cycles, I could never get over people's fascination with making it idle. I suppose there's something to be said for letting the engine idle and warming it up, but that's not a race setting. Warming it up is okay I guess, but you're never going to race at that Temp, or RPM.
Thought was the mixture screw may be a better choice for tuning than the slide needle.....The idle air jet screw does have an effect on the wide open throttle air fuel ratio.Fuel does exit into the air stream thru the small hole on the floor of the venturi just behind the slide throttle valve. Turning the screw out will lean the engine out and turning the screw in will richen the engine up. Of course this has an effect on idle air fuel ratio but also as I explained at wide open throttle. If you ever hear a 206 engine sitting on grid that sounds ratty it probably has the idle air screw turned way in and or the slide needle is in a richer c-clip setting.When the idle air screw is turned all the way in this creates a very high fuel draw signal and fuel flow out the .039" floor hole!
Remember the main jet is .039" and the venturi idle fuel hole is .039" / .013" jet ...........................Hmmmmmmmmmmmmmm...got it?
As they say you don't win races on idle, but the idle settings on the LO206 engine do have an affect under race high rpm conditions.
That's the beauty of the Briggs and Stratton PZ style carburetor, it gives you lots of tuning options! Way to go team DK..........