If the holes are that small (7/64" -1/8"), it shouldn't be the problem. I've been thru all that with my carbs.
You got to get the center carb plates to CLOSE....all the way. The butterfly's must not be straight in the bores or something. Like mentioned, you should be able to loosen off the little brass screws a tad just to get the valves to loosen.
And are you absolutely sure the end carbs are not open a tad as well.....
Hoping to see you get this ironed out and go have some fun...