Damage Assessment of Gear Selector/Shifter Drum

YL82

Perpetual Restorationist
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Complete disassembly of my gear selector drum revealed what appears to be damage in the form of a chunk of metal missing from the end of the drum that the larger bearing fits over (Starwheel end). Not sure how this occurred or when - perhaps before my watch.

I'm wondering whether I should replace my drum. Since the bearing rests over the outer circumference of the face of the drum that covers most of the the "crater", I have to wonder whether it presents any operational issues.

Scores of drums are available on eBay for a wide range of prices. Looks to me like the same drum was used for all XS650 models, although there appears to have been a change in the "Special Shaped Pin" (cam follower pin) sometime in 1976 (my year) when they went away from a shoulder pin and cam follower roller to a straight pin.
 

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I'd clean that out to a nice smooth depression with a easy transition back up to grade and run it, no problem. It's not a significant amount of load bearing area, and should just be smoothed out so it does not become a stress riser. You're a decent dremel job away from no worries in my opinion.
 
I can do that. It's rather jagged, so smoothing it out as you suggest has to help.

I do have access to a world class machine shop, but I have no idea how much can be safely machined/beveled off.

On the other hand, I really need a new Dremel, perhaps one that will accommodate a flex shaft. :D
 
I'd remove as little as practical. I would probably hit it with a half round file or a carbide double cut bit in the dremel and go at it around a 45 degree angle so the smoothing more or less just enlarges the bevel that's already there. as soon as the bottom is clean, I'd break over the top edges smooth all around and call it good. If you have access to a Cratex abrasives kit they would work great for control there.
 
Put it back together just like it is. There is no bearing that runs on that area and the cam retainer will never know it's missing. That cam rotates only about 1/8 turn with each shift so there isn't a lot of load force on it either.
We want it running by spring!
 
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