I thought you folks might be interested in the postmortem I did on my failed final drive. When I got the bike it was making a grumbling sound when you would let off the throttle... So when I did the various spline lubing, I found that the pinion nut was loose... A bunch of shiny stuff as well as some larger pieces came out in the fluid, and cleaning it up and out with a magnet bought me a little time. But the noises returned, and it started sounding like a bad wheel bearing, click-click-click.
So when I got back from my early fathers day ride this morning I decided to tear into it and see just what was up. Here is what I found:

Ring gear and bearings don't look too bad.

Houston, we may have found our problem. :eek2:

Yikes. Boo! :yow

That is one ugly gear, and affirmed that the pieces I was getting out of it were in fact gear teeth. Poor old girl, something knocked out her teeth. I assume it was the loose nut, and a bit of old fashioned final drive neglect.
Change that fluid, heck it's only .25l... I'm using Redline Heavy Shockproof gear lube per a Motobrick member's recommendation. Seems to be working well, I've put on a few hundred miles so far since the change to my new/used final drive. So far so good. :yes