I purchased this Seiko 4205 with aftermarket dial, hands, glass, and bezel from a Seiko flipper on eBay. My expectations were pretty low but had a need for spare parts and a little practice working on a smaller movement so I figured I’d take the chance. It arrived running but it almost looked like second hand was speeding up and slowing down, very strange!
I opened the watch and found rust on the case seal and notable pitting on the caseback itself. Someone left their mark on the inside of the caseback; probably whoever updated this thing with its aftermarket parts.
I took a closer look at the engravings on the balance weight and it looks like one from a 4206 was installed. I am guessing the original was rusted and 4206’s are very cheap sources for a replacement weight.
I decided to just go with it and see where I ended up; onto the timegrapher it went and the results were troubling.
Next, I removed the stem, spacer, and movement from the case.
It looked nice and clean under the bezel but I expected this since the glass and bezel insert looked pretty new.
I had a dial protector on my bench but the hands were too close to the dial to slip it underneath. Instead I used a square of plastic cut from a baggie to protect the dial while I removed the hands.
It’s hard to see in this picture but the dial spacer was both broken and covered in some sort of glue. I’m guessing at some point it was glued to the original movement.
Normally the date wheel should be removed next to avoid bruising its finish. However, this movement is very tiny and the rotor made it very clumsy to get into the movement holder correctly. Before moving on it was important to reduce the chances of an accidental slip up so the autowinding bridge, balance, and reduction wheel were all removed next
With those hazards out of the way it was time to flip the movement back over and get the date disk off to prevent another accident. It is retained by the date disk guard but the date finger is in the way. These were removed next.
It is worth pointing out that the date finger is a plastic part. This one didn’t look good but it is probably still usable. This is a likely source of trouble if the date does not change as the hour hand passes midnight. This is also the little part that causes trouble when you quick set the date between 10pm and 3am.
I went ahead and removed the hour wheel with the date disk. This revealed some pitting from rust underneath. It looks like someone probably removed the rust when the 4206 was serviced and fitted inside this watch. This isn’t good but it could have been worse; like all the other surprises I accepted it and kept going.
The date jumper spring, minute wheel, intermediate date wheel, and date driving wheel are all removed which completes all parts which have been freed by the removal of the date disk guard.
The keyless work was disassembled leaving only the balance jewel. To help keep track of the cap jewel and spring I decided to leave them on the main plate until cleaning time. Actually, I forgot about the cannon pinion here and had to come back for it; c’est la vie!
Just for fun, here is a slightly blurry picture of this jewel from the photos of the next part of this project.
I flipped it back over and next came the train wheel bridge. One of its screws also retained the friction spring for the seconds wheel.
And immediately following that came about half of the wheel train and a few other parts. The tool at the top of the photo is a hand puller which also makes a good cannon pinion puller. The cannon pinion needed to be removed before taking off the center wheel bridge. Since I forgot it earlier I flipped the movement back over and removed it before continuing on.
The sliding crown wheel plate came off next. Of course it was another plastic part.
The pallet fork and its bridge were removed.
Finishing up the mainplate, the center wheel bridge was removed and the remaining parts were piled up.
With the mainplate complete I needed to go back to a couple of things that were set aside. The autowinding bridge needed to be stripped down.
And finally the barrel and mainspring were disassembled. The mainspring looked pretty bad. Kinks were present throughout the entire length, had rust, and the center coil looked ridiculous. Measurements were taken to match a replacement to.
A note about part 2:
I am currently planning to publish the cleaning and reassembly of this watch. However, I ended up breaking the plastic sliding crown wheel plate during reassembly. I sourced a replacement so that I can complete part 2 of this project. Stay tuned…