How does the idle mixture screw work? More specifically, is it turning it in that leans it out, or turning it out that leans it out? When adjusting it, I get about 1.75-2 turns out before the engine starts slowing down but when all the way in it is still idling strong, no change. Any ideas as to what to change? I have the 55 pilot and 152.5 main jets from Lancer in. No white spacer mod yet.

Also, can the screw be replaced? I damaged it a little when I was drilling out the plug.

Yep,...what he said....

There's a spring behind it, so watch out...

In theory,  when adjusting the idle mixture screw, you should be able to get the idle to drop on both the rich side and the lean side.     If you can't, then the jet may need to be replaced.

If you can't get it to drop on the rich side, you need a bigger jet.   If you can't get it to drop on the lean side, smaller jet.    BUT>>>>>>> the sprkplug color should be checked after running on the adjusted setting.

On mine,  the 55 was too big.  I could bottom out the screw and the idle didn't drop.  With the stock jet (52.5), I'm real close to 3 turns out.    ( I could use a 53 or 54 jet)

My bike: stock air box & filter,  White spacer mod, Dyns Screaming Eagle turn-out (clone, w/ baffle added), elevation approx 500 ft above sea level.  152.5 main.