OK, check this one out... My bike is running perfectly and has been for the 4 years I have owned it (2006 YZ450F). Starts first or second kick every time, idles with perfect pitch, no bog anywhere, no decel pop and takes off like a scalded cat.
It also has an aftermarket adjustable fuel screw. Just for fun on my last ride I stopped after about 30 minutes and started playing with the screw. I screwed it all the way both directions with little to no affect on engine idle. At the completely closed position the bike idled just fine and didn't even sputter. Now granted I did not ride it in this mode but it ran fine sitting on the stand.
I intend to not change a thing, however I would like to hear your thoughts on why it doesn't matter on my bike. Also, any way I can damage my baby based on the screw not having the right affect?