shutter won't close at high f/stops

I'm working on a Sputnik Camera for a friend. The shutter blades won't close if the aperture is set smaller than around f/22. Whatever is holding it back is beneath the shutter and I can't see it to troubleshoot. Does anyone have ideas on why this might be? Once it sticks, I can release the shutter blades only by gently moving the aperture back to a wider setting.

Also, is it bad to adjust the aperture while the shutter is open on bulb? When I do this, I feel something sticking and restricting the aperture movement. Eventually whatever it is 'pops' and the aperture can continue to move.

I have another Sputnik and it doesn't have a problem with sticking shutter blades or restriction on the aperture while the blades are open.

Thanks!

Sounds like petrified or sticky lubrication on the backside of the aperture blades, which causes the entire iris to "bow" backwards as it is stopped down and stick to the blades of the leaf shutter.

I have the very same problem with a Kowa SLR with a leaf shutter. I put it in the oven at a very low temp, around 125F and left it there for about 10 minutes and the problem went away until it cooled back down and now, its even worse!

Probably needs the entire shutter cleaned in naphtha or lighter fluid. There is a book on Russian Camera Repair, not cheap but good; do a Google search.

Good luck.

Didn't know that book existed. I'll have to brush up on my Russian. ;-) It looks pretty useful.

Your theory sounds pretty good. The bowing coupled with an aperture wheel that probably isn't completely flat is a good guess.

I've been drowning things in lighter fluid. Looks like I'll keep trying until the book arrives.

Anyone else have other ideas?