OK, as I said, I'm not familiar with that Zenith carb model. I do recall that the Zenith updraft carb used on the Model A's had a fuel adjustment on them, incorporated with the choke. Pull for choke and turn for more fuel when the choke is closed. That could be done on the fly from inside. Just accompanied a Model A back from that show that had issues with the engine running too lean and backfiring. A main jet adjustment took care of that.
