There is a little knob for fast idle on the side of the carb below the choke knob, thread that in a few turns and see if raising the idle helps at all as it could be that it is set too low. Failing that, I would return it to the dealer or at least to another Yamaha dealer close by if you don't trust your purchasing dealer and have them check out the carb for you. There is nothing electrical on the choke that would shut off the engine, just that when you come off the primer circuit (choke) the idle circuit must be plugged or out of adjustment. Best let a dealer clean / reset this if it is still under warranty as you can void the warranty if you were to cause any damage to the engine due to carb settings. Best of luck and hope its just the low idle setting!