let the engine idle for about 10-15 seconds. Then jab the throttle, if it chokes and a plume of smoke comes out it is too rich...if it has little smoke and revs up it may be too lean. It should idle good, set the carb idle screw at about 2-5mm. Then adjust the low speed needle, if it idles too quickly and it revs up buy itself, then it is too lean, if the idle is too low and dies, then lean it just a bit, go by 1/8 increments then fine tune with 1/16 increments.