Well, parts cleaning continues and I've stumbled upon yet another (albeit common) issue. The Clutch adjuster in the left side cover has cracked and is missing a significant check of the sleeve. This is almost certainly due to years of poor to no maintenance of the clutch mechanism. Amazingly, the clutch push rod is still in one piece and the ball bearing was still present and accounted for.
After spending most of my Tuesday hunting for a replacement clutch adjuster, I finally found a bike shop in Michigan that is sitting on a small hoard of brand new ones. $30 later, I have a shiny new adjuster on it's way. This of course, will promptly go into my blue CB500 and the used one from that will get moved to this bike.
For any other CB500 owners out there in need of this part, here's the details:
Honda part #: 22841-266-000 - Adjuster Clutch
Part #5 in the fiche
Available at College Bike Shop
1 (517) 484-6413
http://www.collegebikeshop.com/There were 7 of these left after I ordered mine.