When you said they were rebuilt, could you tell us what the dealer installed in terms of main and pilot jets along with the type of needles and if they were shimmed. You may have to pull off the float bowls to see what is in your carbs.
Because the bike won't start even with the choke pulled I'd say something is messed up or you have a big vacuum leak as already been stated. The choke is really an enricher that allows extra fuel to be drawn into the engine through another series of feed holes. You shouldn't have to open the throttle (unless you are really really rich?).
The next thing is to know what modifications have been done to the exhaust and intake. That will dictate what you should have in place.
I would agree with Ed and richen the two idle/pilot mixture screws, one under each carb. You might want to pull the plugs to see if you really are too lean. White = lean, Black = rich.
