If the Copal SV and MXV shutters in your camera (seen in Yashica TLR’s, among others) doesn’t fire, fires but is sticky on slow speeds, or has otherwise broken, chances are it’s a fault in the self timer. Thankfully there’s a easy fix; just take the self timer out. Unless you know what your doing, in which case you wouldn’t bother reading this post, it’s not worth the effort to try and fix and given the frequency with which the self timer jams you shouldn’t be using it anyway.
Small flathead screwdriver set, 1 cotton swab, patience, PVA glue (to re-attach the camera wrap).
Peel the leatherette off the front focus assembly. Don’t pry against the edge of the frame or you’ll scratch and ding the lightweight metal. Just wedge the tip of a broad thin screwdriver under one edge and once there’s enough worked up to grab onto pull it up carefully with your fingers.
Remove the four largest screws. Once those are out you can lift off the front assembly all in one unit. You can leave those screws for later and work with the camera body attached but it’s easier to lose screws if they drop to the table from the extra two inches or so the body adds. Once it’s off put the body aside. (I didn’t do this but I’ve no fear of losing screws).
Now remove the little screws that hold the front focus assembly cover, the ones on the outside edge of the unit. Once those are off you may lift off the thing metal trim piece.
Now remove the even smaller screws that hold the bay 1 lens covers and aperture and shutter speed knobs. Lift that off to expose the shutter and lens assembly.
Carefully twist off and set aside the tacking lens. This is actually only one half of the tacking lens, the rest is on the underside below the shutter blades. The lower (film-side) taking lens elements can be left in place.
Give the small silver retaining screw that was hidden under the front element of the taking lens a half screw so that it no longer keeps the scalloped retaining ring locked. Once thats done take and pull off the fuzzy end of your cotton swab so that you have a blunt, paper stick. Push the blunt end into one of the scallops, with a little pressure you should be able to unscrew the retaining ring without scratching or bending anything.
Pull off the marked speed and aperture ring. Once thats out of the way you can lift off the speed cam. Getting it off is a bit easier if you open the aperture up all the way.
First pull off the spring arm that rests on top of the self timer escapement, its on the right side. Then locate the small black post with a lock ring on it, Place your finger lightly over it and carefully pry it off with a small screwdriver. Finally check to see if your shutter has a lock-screw holding the self timer escapement in place, if it does it will be at the far left of the escapement, on the inside near the lens mount. If you see a screw there, give it a quarter turn to release the self timer.
Slowly and carefully remove the self timer escapement from the shutter assembly. It will lift straight up. When it catches on the threaded lens mount cock the self timer lever until it’s toothed gear presents it’s flat side to the lens mount, that will free it up to lift out.
Use the lever that projects straight down from the rear of the shutter to cock it and test the shutter a few times. If it all goes well place the speed cam back on and hold it in place while testing the other speeds, they should all fire without lag but the timing accuracy is dependent on the springs strength. If all goes well re-assemble the shutter and reinstall the whole unit.