There can only be a handful of issues since it's a new bike.
Check whether petrol is there in tank and it's coming in carb by removing the fuel pipe attached to carb (yes i know it sounds a bit stupid but just in case)
Secondly does the bike turn off immediately after you put the choke down are you giving it race when you are closing the choke or is it idle ? I am just saying cuz there is a possibility that your idle rpm is set too low and whenever you let go off the race the bike stalls.
Try to keep on giving the race when closing the choke if it doesn't stall that means your idle is set tool low which you can obviously increase by turning the big grey screw on the right side on carb a few degrees clockwise to increase the idle rpm.
Thirdly it may be getting starved of fuel the mixture set is too lean and not enough petrol is reaching the engine. For that is the small golden screw next to the idle one (but i would advise to get it adjusted from mechanic as it's adjustment is a bit complicated)
Lastly it can be a tappet issue again since its a new bike so only slight adjustment is needed and the issue will be resolved.
