Overall the carb looks very good. The problem could be attributed to a tolerance stackup and my bet is the needle seats OK when the carb is produced. After a time, the soft needle tip takes a set and the needle travels a few thousands further towards the seat. The fork can no longer travel far enough to maintain seat pressure ....... because the housing is in the way.

I rectified the problem by simply using a new 3/16" or slightly larger ball end mill just twisted in my fingers and centered over the needle opening to remove enough material to allow the necessary fork and needle travel. The end mill easily and cleanly cut away enough material to do the job. Sadly, after cleanup, reassembly and pressure testing, I didn't want to disassemble the carb again so there is no "after" photo. Pop off pressure is now somewhere north of 25 pounds and reseat about 20 where it holds. This is typical pop-off for these carbs and is not critical for our use unless it is low.

Looking back, if just that little ridge on the housing around the top of the needle was removed, I think the carb would be OK though with needle and seat wear, even removing that might not be enough for a long term repair. Sadly with all the cold and snow outside, I won't know whether my fix was completely successful until sometime next spring! Oh well, such is life in snow country.