Some Jsolettes, most actually, suffer from sticky (green) lubricant. This might mainly be a problem with the focus thread but also can affect the shutter at slower shutter speeds.
The fix for the focus thread is pretty simple. You slowly warm the camera up, not hot, just to the touch. This makes the sticky green stuff somewhat softer. Now you want to turn the focus ring back a forth with mild force. If possible, move it all the way to close focus. Now apply some lighter fluid to the threads, this is a solvent that is compatible with optics. I use the one by Zippo with great success. Use gloves if you don’t want temporary white skin. Now move the focus thread in and out, re-apply lighter fluid if needed. Some stickiness will remain, which is a good thing for the focus ring.
If the shutter times are not OK, the process gets a little bit more involved. Now you will have to remove the lens/shutter-assembly from the camera. You will need a lens spanner to remove the retaining ring on the inside of the camera. It is easiest to first fold the camera, loosen the ring (be careful to not damage the bellows). Unfold the camera and remove the retaining ring. The lens assembly will now pop out to the front.
Similar to large format lenses, the lens consists of a front lens group and a back lens group which are screwed into the shutter.
Unscrew both lens groups. The front ground has to a little stop which needs removal first. This provides the chance of giving those groups a good clean (do not use circular motion at all costs!); lighter fluid is a good solvent for that job.
Speaking of lighter fluid, now it is time to give the shutter/iris assembly a good bath in the same. In problem cases, I washed the assembly in hot water first and when still hot, give it a lighter fluid bath. This will remove all lubrication, which is not good either. Once the iris blades and the gears of the shutter are no longer sticky, dry everything as quickly as possible. We don’t want rust to build up. I now tend to apply small portions of petroleum jelly to the gears (not the aperture blades!). Heat is your friend to distribute the petroleum jelly while moving the mechanisms.
When putting it all together, care should be taken to put the front group in the exact same thread as before. The focus worm has 3 threads. Get the wrong one and all photos will be out of focus. I got that wrong once and found myself with 12 out-of-focus negatives once. With an open shutter, a defined short distance to a bright light source and some parchment paper would will be able to find the correct thread should things have gone wrong.
