I thought about that quite a bit. The needle has a slight taper to it. If you simply unscrew it, it will allow more fuel through at idle, however, at WOT the tip is recessed into the spraybar, thereby impeding clean fuel flow. By shortening it slightly, the taper contacts (or comes close to) the spraybar in the same (screwed in) position even though the actual tip (almost) contacts the inside of the spraybar farther out (obviously 1mm). However because it is shortened, the tip now clears the end of the spraybar, at WOT, which allows full unimpeded flow from the spraybar.

If you just screw it out a ways, then you dont get to screw it in if you need to lean the low end.

Im not technical about this. Im just trying to glean the sensible information off here to get my engine to run well Perhaps this wasnt needed, I also drilled out my fuel nipple/spraybar tube at the same time.

This was a recomendation of XJet. Made good sense to me. Remember what my problem was. I couldnt get the engine to run a rich 4 stroke, even with the needle out in my hand! It was obviously fuel starvation and these seemed to be logical steps to over come that in my case. And they worked, but thats me