The taper on the needle from the kit is also concerning. Look at the massive difference between the 2. the angle might be the same, but the overall length of the taper (the new one being much shorter), might prevent the needle from fully sealing off fuel flow (needle body bottoming out in seat). One thing you can do/test... when you have the float attached to the top half of the carb, flip the top half over so the float is closed from gravity, and try and blow into the carb fuel inlet (block off the return barb with your hand), and see if its fully sealing and not letting any air thru.
On avg, fuel pressure is around 2-4psi, we can only blow about ~1psi, so it should easily seal shut against human breath.