One last theory--when you inspected the orifice plug, did you check the actual orifice diameter? A #72 plug should be 0.072" diameter hole. Lots of misguided folks will drill it out in the theory that more gas will make it go faster.
(Completely revising my previous statement--it was boneheadedly incorrect)
I don't have a wire gauge larger than .03. But I was able to fit a 5/64 drill bit shank through the orifice. That's just a shade over .078. And that was also a loose fit, with considerable slop.
So voila! There's the ruptured dam. That was a great suggestion! To think I was only 1 step away from tossing the whole carb into the trash can...that advice saved it. Thank you!
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