Mamiya 200mm f4 "C" lens for 645: slipping focus ring

I bought a Mamiya 200mm f4 "C" lens for Mamiya 645. Cosmetically it's about mint. However, the Rubber covered focus ring turns freely and the focus is not changing.

If I'm lucky, maybe it's a matter of removing the rubber ring and tightening screws in the barrel (under the rubber ring). If I'm not lucky, the screws may have sheared off. First off, what's the trick in removing the rubber ring without destroying it?

Has anyone else had a similar problem with this lens or another Mamiya 645 lens, and is there a simple fix? The repairman I took it to wasn't sure what the problem was, and to cover himself, the estimate was at least double the replacement cost....so before I toss it, I thought I'd see if i could repair it myself.

Bob.

Not familiar with Mamiya 645 or its lens, but....
The rubber rings on lens come loose and slip. To remove the rubber ring slip a narrow flat blade screwdriver (common screwdriver) between the edge of the rubber and the edge of the ring its on then work the screwdriver under the rubber ring. Lift up and pull out on the ring, slide over to the adjacent area of the ring and repeat until the rubber ring is fully out of the recess its in then work off the lens. A sharp point object such as an ice pick but the chances of damaging the rubber are greatly increased. Once the rubber is off post some pictures of the focus ring if you cannot figure out what's wrong.

And, if it's just the rubber slipping just us a dab or two of contact cement where it goes.
No need for two coats, that's very permanent. A little dab'll do ya Charlie.

It's not just the rubber ring...that's snug against the collar it is fitted onto. It's the metal collar underneath that is slipping. I'll know more when I get it off.
bob.

binglebugbob said:

It's not just the rubber ring...that's snug against the collar it is fitted onto. It's the metal collar underneath that is slipping. I'll know more when I get it off.
bob.

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Hi. did you get to fix this issue? I just bought this lens "as-is" and it has exactly the same problem. I've been looking around for some repair instructions and this is the only thread I see.
I've disassembled most of the lens, but I still have the barrel + the "free-floating" focus ring. I don't see any more screws to take out.

If you remember the steps you took, please give some instructions on how to get it fixed. thank you

I don't know this lens in particular, but based on other lenses and what other people said in the thread: You probably have to remove the rubber focusing ring. You do this as described above, by carefully working a thin screwdriver under the rubber ring to remove it without tearing it. After that, you are likely to discover small screws under the rubber. Often these small screws locate the outer metal ring with respect to an inner body. If the focusing helicoid became stiff due to dried out grease, it is possible that someone turned it hard enough to drag the screws and outer ring out of position, so the outer ring is no longer turning the inner part.

If the above ^^ is the case, then you should really service (or have serviced) the helicoid or you will eventually strip-out the screw indentations due to the high friction in the focus ring.