250-500cc PWK Airstriker idle question

I just switched over to a JD Jetting pre-jetted Keihin PWK Airstriker 38 carb for my 2009 Husqvarna WR300 two-stroke. I am having trouble adjusting the idle. The bike is hard to start now, but starts easily if I open the throttle. Once it is started, it needs the idle adjusted. I followed the air screw adjustment instructions (starting out 1 and 1/2 turns out from seated), but it didn't seem to make a difference (it is hard to tell whether screwing it in or out makes a difference since the bike does not want to idle anyway). It there throttle position setting or something? The JD Jetting instructions only talk about the air screw, and jetting. What does the black screw handle do that is just above the air screw and fuel inlet (it is black with a spring on it)? Please help. Thanks. -Todd

PS: The bike seemed to be jetted pretty well on my short ride (mid and top end), other than the idle adjustments. I can make the bike idle by cracking the throttle and holding it slightly open.

Svttodd, That screw adjusts the idle speed. It sounds like it's screwed out too far and therefor not allowing the engine to idle. Screwing it in lifts the slide just the same as turning the throttle does. Try screwing it in until the bike idles. Then adjust the airscrew.

You may be too rich on the pilot if it won't idle and the idle screw (black) does not do much