interesting post.
http://www.xs650.com/forum/showthread.php?t=5536
I didn't read the whole thing but it looks like he was converting his variable field generator to a fixed field like the Vision has. If he uses a series R/R, he might be on the right track.
Yup, appears to have a kit to transform the tired old charging system components with a permanent magnet type. Nicely done upgrade for the venerable 650 twin. His web site has a few more tasty items for those classic Yamahas too.