If it doesn't idle without the choke, you need to check the carbs again. The pilot circuit is likely gummed up. Remove the pilot jets and clean them thoroughly. There are small holes that need to be totally clear. Also make sure the small passages in the carb are cleaned thoroughly.
I would check your compression. Make sure that the motor has no air leaks in to it. Take carb cleaner and spray around the pto seal and the carburetor intake boots to make sure that there is no issue before going back in to the carbs. If the engine revs up or changes any rpm when spraying then you have an air leak. If there is no rpm change then go back in to the carbs and like ultrajunkie said clean them. Also make sure that your idle screws are set to spec. The idle mixture screws should be at 1 turn out. They are the small screws that are in the front side of the carbs. Make sure that your choke cables are set right as well. There is a small bolt on the front of the crank case as well that you can take out and see if there is anything that comes out of the bottom of the crank case. Make sure that the are put back in tight do not over tighten them. Hope that this helps you our.
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