Is this a new setup ???...Is it an old setup ???...It could be as simple as a stuck choke, it could be dirt/sludge in the carbie if an older setup, it could be a bad float with a pin hole leak in it, causing the float to fill up with fuel, thus holding it down and flooding out.
Is this the stock NT carbie or was it replaced with another type of carbie ???
A little information goes a long way in helping us to help you with your problem rather than guessing at all the scenarios involved...lol...DAMIEN