Motorcycle Repair: CARB low speed jet size, jet size, speed jet

Question
The manual says that the "average" or factory idle speed screw setting is about 2 to 2 1/2 turns out. If the carb still seems to lean at this point is this where you go up a size on the low speed jet? if not how do you size it?
                   thanks
                      Ez  

Answer
You didn't say what kind of bike, what year, what model, what size motor, what carburetor.  Idle screw only adjusts for idle, not running above idle.  Yes idle jet size increase will richen it up AT IDLE and low speed only.  Main jet and needle changes mixture for mid and high rpm.  On newer Keihin carbs the mixture screw increases both air and fuel so it doesn't change the ratio, you have to use a larger idle jet.