Chronograph adjustment question

So I got the 'Bunny' Landeron 48 chronograph back together. When installing the activating lever I bunged the minute jumper. Also missing the piano wire springs on the flyback lever which may be the one I used for the 'goat' Landeron 48.

The issue with both Goat and Bunny is that when I engage the chronograph, the watch ticks for about 15 to 20 seconds then stops.

Should the exentric cams be adjusted? The books and guides state not to turn or remove these as moving them can make them come loose. There are also indications that if one is moved then the others need to be moved as well.
Goat was somewhat corroded, So I can understand that the adjustments might be needed. Bunny on was fairly clearn and recently disasebled before cleaning.

Curious that they both seem to have the same problem.

I have yet to get or make or fix a Timegrapher. The balance seems to have good amplitude, but I do not know if they are in beat. The hands are on Goat and it seems to loose a minute or so a day. Sometimes I forget to wind it.
Could the beat also affect this stopping?

When working on a complex watch, it's best to be 100% sure that any issues in the base movement, such as low balance amplitude, are taken care of before you move ahead and install the chronograph parts. Troubleshooting is a process of elimination, so if you know that the base movement (enough parts to make the watch tick) is in good shape, you have eliminated a bunch of things before you start assembling the chronograph.

So not knowing what the amplitude is will make it more difficult to give advice, because it may be that the amplitude is just too low. Also, there is typically an acceptable level of amplitude drop that occurs when the chronograph is engaged, so even if you end up getting it working, you won't know if it's correct.

So moving past that, if it's stopping soon after you start it, I would first examine the teeth of all the wheel involved to see if there is any debris in them or damage to them that might be causing them to jam. I would also look at the pivots and make sure they are in good condition, and that no long posts are bent.

If all that is good, then it's possible that the depth of engagement of the teeth of the driving wheel to the coupling wheel, and/or the coupling wheel to the chronograph wheel, is too deep.

Here is a chronograph where the drive wheel and coupling wheel spacing is too deep:



Also too deep where the coupling wheel and chronograph wheel mesh:



The first one above was adjusted so that the teeth of the coupling wheel are about 2/3 of the way into the teeth of the drive wheel:



And the coupling wheel teeth are adjusted so that they are about 1/3 into the chronograph wheel teeth:



You don't want them to bottom out or come anywhere near that.

Hope this helps.

Cheers, Al

To add to this excellent advice, check that all wheels are not bent and run flat. I also had problems once with a driving wheel which was too high on its post. As it is removable (and sometime it's post is bent) , it is worth to double check if it is correctly put back, and flat.

Personally on a chrono in such rough shape l do as archer said : I do the base movement, even letting it run for some time and regulating it before adding the chrono parts. Maybe keep it in mind for the next time.

Exactly the sort of advice I was looking for.

I have been letting the base movements run before adding back the chronograph parts. I have not taken the time to check all the details of the base unit such as the polish of the pivots.

I also really apriciate the clear photographs, that explain the written text in the text books. I need to use my microscope cameras more to see details such as those shown.