I knew the older regulators were mechanical, but I had never heard of them being adjustable -- makes sense, though. My truck had an original, mechanical regulator which went out on me, a couple of months ago. I replaced it with a solid-state unit (current replacement from the parts store), and that works perfectly. I guess I would just replace a mechanical unit for a solid-state, modern type, as they work more reliably, no adjustments necessary, nor possible. YMMV. It is interesting, though. Thanks for sharing. Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII