Service: Longines Ultra-Chron calibre 431

IMG_2870Wynand sent in this Longines Ultra-Chron for a service. You have to love these watches. Not only do they look great, but they have a snappy date, are automatic, and, last but not least, tick with 36,000 bph!


This could look a bit better.IMG_2873

Looks like somebody deformed the case back gasket when putting the watch together, so it was never even water resistant in the slightest.IMG_2875

The movement is held in place by a ring that grips into the case. Somebody put a plastic gasket in there, and it doesn’t belong there at all. He probably put the retaining ring into the wrong groove…IMG_2876

Dial and hands are in great shape.IMG_2877

Bottom plate with date ring.IMG_2881The automatic winding mechanism.IMG_2893

Nothing I can do about the mainspring, as you can’t open the barrel. I put it to the side, as I don’t want to put it through the cleaning machine. The cleaning fluid would just build up inside, and not flush out.IMG_2898

The components of the snappy date changer.IMG_2902

In the bottom right basket, you can see the retaining ring that holds the movement in the case.IMG_3181

The base movement is back together, and beating 10 times per second!

The barrel arbor screw that was in place was too small, and slipped when I tried to tighten it. I find a 0.8mm thread screw in my spare parts drawer, and put it in.IMG_3190

Considering that I didn’t change the mainspring (you can’t get those barrels for love nor money), and that the movement has just been put together, this is looking rather good.IMG_3184

Now I start on the bottom plate.IMG_3189

The movement back in the case, and sitting firmly without the plastic ring that was there before.IMG_3191

Great looking watch – got to get one of these one day!

13 thoughts on “Service: Longines Ultra-Chron calibre 431

  1. Flagship/431- Ultrachron: I have found the auto-wind failing to work as well as before, and I’ve been winding manually. But that too is getting increasingly creaky and I don’t want to force anything. I have assumed from various posts that the barrel is in need of replacement (?).
    So I have purchased a NOS sealed barrel (part No 180/1) in the hopes that it will solve the problem. All I need now is a watchmaker to install it !

  2. Good job, nice done. By the way, a friend of mine gave me the same model to be restored. Someone broke the tip of the balance axis and after a hard pursuit I found a donor. My question is: can I have a not original crystal to replace the old and battered one. Thank you so much and keep working this way.

  3. I have a very similar watch.

    Longines, ultra chron, automatic, date & winder.

    Time: 6, 9 & 12 are not as obviously different.
    Swiss: No mention of ‘Swiss made’ on front.
    Colour: Yellow gold.

    Back case: Use 1260 wrench
    14K gold,

    Started working itself after 12 years in the drawer.

    Of exact model / possible value / best place to sell etc… would I need certificate etc…

    If you add an email I can send pics

  4. I have a Flagship Ultrachron in very fine condition which was properly serviced about 10 years ago in Switzerland since which it keeps perfect time, virtually to Chronometer standards. The only problem is the Rotor bearing has developed play and when rotated makes light scraping contact with the movement. How easy is it to replace the bearing? I removed the Rotor itself and the bearing outer is firmly in place so I assume the problem is simply that it is worn or damaged even though the balls are all present. Any advice welcome

  5. I’ll give you a pound to take one of them barrels apart and film what happens 😉

    Someone must have come with a procedure for replacing the mainspring… I dont like to think that such watches might one day be unrepairable just for lack of the whole assembly.

      • I think somebody of Christians ability showing such caution to that task tells me everything as a ham fisted individual like myself.

        Would be interesting but I presume could be quite dangerous.

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