My bike runs better with the choke pulled 1/4 way out.
In the carb there are 2 jets, Main jet, and Slow jet.
Main jet opens up when you twist the throttle, and slow jet is fixed for idle.
There is an idle screw on the exterior of the carb as well as a pilot screw (??). The pilot screw is supposed to be screwed all the way in and then out 2 turns. (there is a more technical way of adjusting this, requiring a portable tachometer, which I dont have.)
Any idea as to what can cause this "must have choke" situation?