Mjd-djm
Established
I’ve just picked up an M6 TTL and on some of my lenses the lens focus is not smooth and gets quite tight especially when you get down to close focus. They all focus nice and smooth on my M4. Is there something wrong with my coupling wheel? Anyone else ever experienced this? Is there a fix?
retinax
Well-known
Can you report what happens when you gently push the RF arm and rotate the wheel with your finger? That might help the experts here, or maybe yourself, see what's going on I think. That it gets tight on close focus rather than towards infinity is weird though. Which lenses have the issue? Do they have large rear elements? Is the RF accurate when it happens, showing the correct distance? If not, the RF arm might be bent and the riding somewhere that's not the RF cam.
Mjd-djm
Established
It’s especially noticeable on my Zeiss 35mm 2.8 and also my collapsible summicron. Much better on my 50mm skopar and 50mm v4 cron.
retinax
Well-known
Are you waiting for your lawyer? We can help better if you disclose more information. 
Mjd-djm
Established
Lol, ok so when I gently push the RF arm and rotate it moves freely, although it is definitely stiffer than my M4 which is very easy to move. It doesn’t appear bent. When I release it it feels as if it wants to return with more force than on the M4. When focusing with the Zeiss 35mm 2.8 biogon the focus is slightly tighter throughout the whole range but when you get to closer focus distances (between 1m and 0.7m) it almost gets stuck and needs to be forced. Outside of the 1m range it gets ‘relatively’ loose again.
I don't really know that much about Leicas (yet) but if you set the camera to "B" and fit a lockable cable release, you ought to be able to observe the components as lenses are focused. This may inform your understanding of the issue(s).
Dralowid
Michael
Obvious but have you checked that the lens in question moves freely when not on the camera?
presspass
filmshooter
I have had two M6ttl cameras since new. Both could reproduce the problem you report until they had CLAs done by Don Goldberg about eight years ago. Since then, they are the smoothest Ms I shoot. BTW, there are some conflicts with Zeiss lenses and some M bodies - I have a Solms M6 that will not mount my Sonnar 50 1.5 but the lens will mount fine on everything else.