It does sound like you are a bit too rich on the bottom.
Try taking a set of needle nose & pinching your fuel line going to the carb, as you try to start it .It may take a few try to clear out the flooding but If it does get better or even stop back firing ,, then make a small adjustment to the bottom needle.
Just one other thing you can check. Make sure your pressure line blows free and clear.
That has caused some headaches in the pits before.