I picked up an as-is GSN for $2 the other day. It had some issues like a bent filter ring, some mild lens fungus and a dented hot shoe. I fixed the fungus and filter ring damage (not too worried about the hot shoe)
The only issue left is that the shutter is not opening all the way while firing. I disassembled the lens, cleaned the blades with Ronson and lubed the mech with oil. But I'm still having the same issues with the shutter not opening completely. In fact it seems that my cleaning and lubing had NO affect on the shutter.
I can get them to open by putting pressure on the cams so I know its not an obstruction. I'm really out of ideas on this one.
You might want to contact Russ Sisco, info@camerarefurb.com. I've used him for Yashica clas (as well as Mark Hama) he probably would know what the problem is and what you can do to fix it.
I took apart the lens, cleaned each blade by hand and I also did the same with all the individual springs and cams, when I assembled it back together it worked. I have no idea what I did, maybe some small bit of dust or sand, who knows.
I also cleaned and greased the helical focusing gear and other minor things.
I have an idea about what caused the sticky blades: capillary action.
After I cleaned the blades on *my* GSN, the shutter wouldn't even open! I thought I'd wrecked it. Wait ten minutes for the Ronson to evaporate and it was no worse off than before. Which is to say, still in need of cleaning. I finally used a Q-tip saturated with Ronson and repeated firings to get all the oil off. Works great, now. And I learned that those blades are so close together and so light, that any liquid will suck right in between them and freeze them right up.