When you say you've cleaned the carb, have you stripped it down and cleaned the jets? You have an idle process on the carb which may have a fault, ie blocked, but that is rare. What you may have is an air leak which is between the carb and the inlet manifold. I would suggest that you check any pipes that are connected to the inlet manifold to make sure that they are not disconnected or split, as this would result in a weak mixture which results in the engine stalling on idle. If you are absolutely sure that there are no air leaks then it may be that your ignition timing is slightly out, or that you have a fault in the carb.