Having taken apart the driver's side door lock and have coil springs, flat steel springs and various parts fly all over the shop, I thought I would share my experience with you. Attached are two photos of the door lock assembly (less the metal cover plate) 'front' and 'back'. On the 'front' photo, at the lower left you can see a spring and plastic cylinder pressing against the bottom of the pivot with the 'hook' on the lower end. This hook engages the round lock capture. The lock capture is shown in the 'door closed' position. To the left side you see a vertical black piece - this is a steel spring that presses against a rod with a bow in it that is shown on the 'back' photo. At the top of the spring is a lever that I call a 'child lock' - with the lever in the position shown, the door cannot be opened from the inside. By rotating the lever clockwise, you can then open the door from the inside. Don't know exactly why Chapman included this feature. On the 'back' photo you can see the 'door open' lever arm at the top - it does not have a control rod connected to it. The upper rod connects to the inside door handle 'lock' rotating tab, the lower rod connects to the key lock. The key lock control rod in installed under the metal of the back plate and has a bow in it that presses against the steel spring shown on the 'front' photo. The back plate can be removed from the plastic housing my pressing out the 'dowel' piece shown at the center on the metal back plate. I have taken the lock apart as it was full of 'gunk' and needed to be cleaned out and lubed - used a little bit of wheel bearing grease for lube. This lock is off of my 1974 Twin Cam Special but I think the same lock is used on the Twin Cam and S2 models, but not the S1 models.
