John I think you're onto something. I measured the slot depth at the back of the fiber gear at .100" and the slot at the back of the steel gear at ~.090". The key appeared to be canted slightly upward at the back (and a mike job confirmed that) and there seems to some evidence of binding along its top at the back as well.

However before you take my measurements to the bank, I have a confession to make. I remeasured the thickness of the spacer ring and found it not to be the .143" I measured earlier but .159", essentially identical to what George Downs measured. I'm not sure how I managed to make that mistake, but clearly I did. So it appears I don't need a new ring - just a new eyeglass prescription.

So now I'm going to take a deep breath and dress the key-way in the steel gear ever so slightly, make sure the key is level front to back and try again.

Watch this space.

--
Barry '67 122S "Betty", '69 122S "Veronica"