Re: Idle adjustment on rochester 2 bl. carb
And yet some more thoughts. The idle adjustment is a combination of throttle plate position and mixture screw adjustment. The idle mixture 'circuit' is a small passageway in the carb that is 'activated' when the throttle plates are in their proper 'idle' position. Air is pulled through this passageway and 'mixed' with fuel and dumped in the carb below the throttle plates. When the throttle is opened the idle circuit no longer functions and the carb now gets it fuel from the main circuit. Yes the plates have to be open a little and there is a 'spec' for that, but if open too far the idle circuit won't work. Don't be too afraid of "touching" the idle mixture screws... my I6 runs best at about 1/4 turn out on both screws. Do this: after making sure all of the linkage is returning throttle plates (nearly)closed, and the timing is correct, and with the engine warm, turn in each screw until it lightly seats. The engine should stumble and probably stop if the throttle plates are closed and in their proper position. If the engine does not stop, then you are probably 'leaking' too much air/fuel past the throttle plates. If the engine stops, then back off the screws about 1 to 1 1/2 turns and start the engine. Now turn in each screw until the engine starts to stumble then back it off to where it runs smooth... do one at a time, and turn only a little bit.
) Look at the linkage, that's where the idle speed screw is.