have you tried shooting some fuel oil mix in the carb directly to see how the engine reacts...if it run whith no choke it confirms the engine is not pulling it's own fuel fuel out of the carbs . I just saw the question about shooting fuel in carb to see how engine reacts.
do these carbs have any adjustmenta common issue would also be the small "idle pickup" tube in the middle of the emulsion tube that carries fuel to the upper idle chamber. its like a tiny straw (works at low vacuum) vs a larger one (only works at higher vacuum because of the larger diameter). this tube must be clean. another thing i always do is turn the carb upside down and blow into the fuel inlet nipple. you shouldn't hear or feel ANY slow leaks. now tip it right side up and blow. should be super easy to blow into. these will not run if the idle air orifice is missing... wont suck up any fuel from idle pickup tube as mentioned.