Having the idle air screw turned in that far, and your earlier comment about having to choke it to make it idle tells me that it is running lean (at least on idle). Now that you have it idling without the choke, try lightly applying the choke (with the engine warm). It should make it want to die out. If it doesn't, then it's definitely too lean on idle and likely needs the carbs gone through again, or it's possible you have an air leak somewhere.