Sounds like a lean condition , meaning its getting to much air and not enough fuel. Possible air leak at the carb and intake connection ? Got any starting fluid or wd-40 ? Start the bike and let it idle , spray a small amount of either spray around the intake and carb connection. If you have an air leak your engine rpms will change. With starting fluid the rpms will increase and with wd-40 the rpms will decrease.
Add it to your list of things to check along with the other members advice.
Welcome to the world of motorized bicycle !