What I was told by someone whose worked on bikes and cars all his life is that the modern lead-free fuel leaves an 'emulsion' like a kind of varnish, on the carb parts including the jets. I've had problems with my Kwak after winter layups and usually cure it by shoving in an overdose of 'fuel system cleaner'. Whether or not that's the problem, the cure works.
However as that's not the problem with the XVS it's irrelevant.
Yup, it's pain in the parts , particularly noticeable on 4 barrel carbs as it often causes flooding after even a short layup...and the ethanol percentage is set tp increase shortly:(