Introduce and question

[Geraint]

Hi, My name is G and I have been teaching myself for the past 18 months.  I have a Lemania cal 1275 that I have just finished.  The problem that I have is when I start the chronograph, the watch will run for a few minutes on the wrist then stop.  If the watch is face up on the bench it will run until the power runs out.  If the chronograph is off the watch runs great.  The mainspring is the original and I think it has lost its power.  On Ranfft spring size is 1.30 x 10.5 x 0.13 x 300 but on cousins spring size is 1.30 x .12 x 320 x 10 ???   So if anyone could help as I don't want to strip the watch only to use the wrong size spring.  If there could be something else going on please advise as I am still learning and keen to hear any suggestions.

Thanks 

G 

[AndyGSi]

Welcome to the forum

As always there's normally so slight variations between sources so you're always best measuring what's already fitted.

So far I've found the following

Emmy = 1.30 x .12 x 320

Boley show as a GR3285 which on Cousins = Omega 320 1.30 x .11 x 340

You could also check out this post.

 

[Geraint]

Thanks for this.

G