SETTING THE IDLE: DON'T CHANGE THE IDLE UNTIL YOU HAVE RUN THE ENGINE-IT IS ALREADY SET. Your idle setting should be fairly close from the factory, so try it as-is first. Look at the nut holding the throttle arm. The idle needle should be about flush (even) with the end of the nut. If not, this is a good place to start. (my experience is that this position is about 1/2 to 3/4 turns rich, but start here anyway)
Open the throttle and set the high speed to about 500 below peak. (see below) Warm the engine and pull the throttle back. Set the throttle at 1/3 open, i.e. the opening should be about 1/8" (3 mm) wide. Let the engine run and stabilize for 10 seconds. Pinch the fuel line closed. Does the engine speed up and die? If so, it's too richturn the idle in (clockwise) 1/4 turn. Repeat, warming at full throttle, pulling back to 1/3 throttle, allowing the engine to stabilize for 10 sec, pinching the tubing until the engine dies within 1-2 seconds. At this point, the carb should be within 1/4 turn of correct.
Open the throttle and warm the engine. Pull the throttle back to idle for a few seconds. Push the throttle slowly to full. If the transition is not smooth, or if the engine stalls (except for a slight pause to pipe up) try 1/8 turn leaner. If the idle is too lean, the engine will not transition past the 1/3 open point without sagging or dying. Continue this procedure, moving only 1/8 turn increments of the idle needle until you have a slow, reliable idle and a rapid transition. Remember, warm the engine before working with the idle and transition settings. Occasionally, someone gets the idle so lean that the high speed will not work. Open the idle needle and start over if this happens.