assuming you have no air leaks the way to do it is this-get a dressmaking pin and close the throttle barrell down until it is pinching the pin,then wind the slow running adjuster in until it seats,attach a clean piece of fuel pipe to engine fuel inlet. blow down the pipe,keep the pressure up and slowly undo the adjuster until you feel pressure releasing in the pipe-you may hear it first,when this is done it will be spot on.p.s. don't forget to take the pin out!!