This is very embarassing. I'm not sure why I am sharing it.
Upon opening the carb on the right side, I found the metal plate and the four screws that hold down the base of the diaphragm loose; or, rather, NOT installed - just sitting in there, loose.
I had taken both carbs home to work on them. I reassembled both, but before finishing the right one, I suddenly relaized I was late for a Zoom meeting that I was leading. So, I put the plate ands crews inside the carb, replaced the top and threaded the screws on just tight enough by hand to keep anything from falling out - I would do the final asembly at the hangar later that day.
Well several days went by without gettng back to the job, and when I did, I just installed both carbs. Didn't remember the right one needed just a bit more work first.
Conclusion: I have way too many distractions when I'm home with wife and dogs and cats, and the ringing of the phone with all the political solicitation calls. The hangar is quiet, more or less free of distractions (especially if I park around the corner and lock the door!).
