Here's some information about the passages in the carbs:
https://n4mwd.blogspot.com/2013/10/s...-passages.html
Or PM ducatiman and ask about his service. He's expert in restoring these carbs to new condition. He did mine for me a couple years ago.
He's right that the problem is likely clogged idle circuits. The compression test is worth doing anyway, because as I've said before, if your valves are out of spec, you'll be chasing carb problems forever.