It's always something...

...and now there's this:

The little broken tab indicated by the arrow, is, as far as I can tell, the only thing that keeps the sprocket from sliding around on the shaft.  Is there supposed to be something else that was already missing when I got it?  I don't see any indication of another part in the manuals or the parts diagrams.  Would it be possible to use some kind of washer behind the sprocket?  Somehow it doesn't seem so unless you could be sure it wouldn't wear out and become a bunch of metal shavings in the crankcase, which wouldn't be too cool.

The sprocket doesn't slide so far that the rollers and springs fall out of the starter clutch...but almost.  However, it does slide far enough that the chain has worn a groove in the casting, and that doesn't seem like a good thing

So... what to do about this?  Have looked at several parts sites on the web and they either list the part as "not available" or don't list it at all. 

It's so tedious trying to find something like this on E-Bay.  I looked through 17 pages of CB500 parts yesterday, and the closest thing I saw would involve buying a box of mixed junk and trusting to providence that the part i needed just happened to be miraculously one of the parts in the box.  (They used to sell "grab bags" at a little store near my Grandpa's shop when I was a kid.  ...my cousin Billy and I used to bum change and buy them.  Seemed that Billy always got the good stuff, so I'm not real big on grab bags.)

Got a feeler out on a motorcycle maintenance forum for a part or advice, and I still haven't decided what I'm doing about the last problem.

Been back from vacation for almost 2 weeks now and not making a whole lot of progress so it looks like my estimate of 3 weeks was overly optimistic....but then I've always been a 'half-full-kind-of-guy.'