Take the whole four carbs off, turn em upside down, remove all the throttle blade ( Idle speed ) adjuster screws and close each pair of throttle blades-- note the closed position in relation to the port with the idle mixture screws. They should all be a similar distance & the thottle blade/s of your problem carb may need to be repositioned in the shaft to obtain the correct idle mixture port/blade relationship. Shouldnt happen, but it does. There is a cure--- its called H****Y.
