84 200X Pilot screw...help

[waterfowler]

Can anyone tell me exactly what the pilot screw does? I am making final adjustments to my X and the book says 2 1/4 turns out but also says for tuning, close till trike stops running then back out 360*. It runs great at RPM, but seems to be idling irratically. Close enough to ride though :)
Thanks,

[Dirtcrasher]

Pilot screw on my HONDA 250SX when turned in lets less gas in and more when turned out. At 35 degress I could not even start it until I turned it out an additional turn than the book suggested. I thought something was wrong with the used carb I got but it was the pilot screw that wouldn't let it start. I believe it affects start up and initial throttle response.