Can you verify that the choke is actually closing when you pull on the cable? If it doesn't close all the way, it isn't doing squat while you crank and it won't be pulling fuel out of the bowl. Try removing the air cleaner and holding your hand over the carb while you crank it, this will act like a choke to pull in fuel. (Be prepared to remove your hand when it fires)
Also make sure your float bowl level is adjusted correctly, you may not not have enough vacuum at cranking to pull fuel out of the bowl.
