Breitling Navitimer 806

[Bonefixer]

A friend of a friend has entrusted me with the service/restoration of what was his grandfather's Breitling Navitimer 806. It was just lying around in a drawer, missing its glass and two of the hands, but incredibly it runs and the Chrono seems to function. 
 

I've started dismantling it and have learned that I'm not the worst amateur watch fixer in the world - the dial had been glued down!

 I'm planning to strip down and clean the movement - I should be competent to do that. Clean and re-lume the hands. Source a new glass - acrylic I think - and do very little to the dial apart from maybe a cotton bud and water. 
 

Any advice from the good people here before I crack on? I did tell him the potential value of this and suggest he might get a proper watch maker to sort it. I've offered no guarantees apart from I shouldn't make it worse. 

[Mercurial]

It can be difficult to keep track of all the different screws on a movement like this, you can save yourself a lot of trouble by putting each screw back on the movement after removing the part it secures. 

This ensures every screw stays in the position you found it in, but if the watch was serviced by someone willing to glue the dial on, it’s possible that some of the screws are already misplaced.

You mentioned that the chronograph functions. That being the case, I suggest you keep all the eccentrics that adjust the depthing and engagement of the chronograph works in the position they’re in, unless you have experience with setting up and adjusting a chronograph. 

Take plenty of photos, and you should be fine during reassembly. 

I hope that helps,

Mark

[rehajm]

…watch the YouTubers who have serviced this one, maybe a couple of times.  It helps to be familiar when you dive in. Also can help when you forget where that screw goes…

[Bonefixer]

Update!

 I've dismantled it, cleaned all the glue off, and rebuilt and lubricated the base movement. I'll leave the chrono part for another day. It's running well - great amplitude and keeping time, but it's got a beat error of 4.8ms. 
 

How important is it to correct this? I'm worried that the potential for making things worse having to take the hairspring off and on repeatedly to adjust this. Would anyone here accept it at that?

[LittleWatchShop]

16 minutes ago, Bonefixer said:

How important is it to correct this? I'm worried that the potential for making things worse having to take the hairspring off and on repeatedly to adjust this. Would anyone here accept it at that?

I am an amateur, so there's that. I do not get fixated on amplitude, lift angles, and beat error. However, 4.8ms would bug me if it were my watch. But you must judge your own skills to appreciate the possibility of going backward. I suggest, that you button it up let your friend enjoy the watch for now. As your skills progress, come back to it and correct it.

I assume that this watch has a fixed hairspring pin. Some modern watches have an adjustable pin along with adjustable regulator. These are trivial to get in beat.

On 4/4/2025 at 10:19 PM, Mercurial said:

It can be difficult to keep track of all the different screws on a movement like this, you can save yourself a lot of trouble by putting each screw back on the movement after removing the part it secures. 

I own a valjoux 726 my dad gave me on my 18th birthday (a looooong time ago). I broke the ratchet wheel with an aggressive wind 4 yrs ago. I have been waiting for my skills to progress before doing a service. I am close. Your advice is well placed and I will apply it.

[watchweasol]

Hi. What’s the movement. ETA. 7750 etc as a service sheets would be handy to have for reference.

[Bonefixer]

Venus 178