Canon 28mm 2.8 LTM focusing issue

[jmp]

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Unfortunately, I don't have access to any M240

[Pyrogallol]

It does sound as if it has been taken apart and reassembled wrong. I think you should return it if you can. I have had one or two eBay purchases with similar problems that I have returned.

Edited January 15, 2023 by Pyrogallol

[jmp]

Update: I have managed to fix the problem.

Indeed the issue was coming from a wrong reassembly of the rear helicoid (the one driving the telemeter). After a bit of try and test, I managed to find the right spot and now infinity is on focus when on the infinity lock and distances are right on the focus ring.

For the record, I have also found some informations on old Canon lenses where the infinity can be finely tuned using an inner shim. I have tried this method but my lens' shift was too large to be fixed like this. But the method is valid for smaller shift.

check here (in Japanese)  https://mglss.rakugan.com/

While opened, I also took the opportunity to make a good cleaning and lubing, so it's almost as good as new