Re: Carb issues
All that screw does is set the idle speed. It does so by raising or lowering the lowest point that the throttle slide will drop to.
I'd bet you're running too rich. Most of these do from the box. You can adjust the mixture a little bit by pulling the throttle slide out, taking the slide off the cable, and adjusting the little e-clip on the throttle needle. Move that clip higher on the needle to reduce the amount of fuel (make it leaner), and you'll probably be able to idle with the throttle slide more closed.
But really, for now, if it does idle and you have throttle response - go ride it!