My speedy 861 has started to stop after only six hours or so after a full wind, it also doesnt seem to have a stop point any more while winding, i wound it this morning 70 turns but easily could have gone on, i did notice that the crown does turn back a little on release after each turn when i would guess it was getting close to fully wound ? ive put it up against my 1861 which is fully wound after only 23 turns, so im sure somethings not right. any ideas ?

 

Sounds like a broken mainspring.

 

Yep mine went last year same kind of senario.
I sent mine to STS UK and Simon Freese says broken main spring is a common fault with the earlier 861's

 

Common on all manual winding Speedmasters...I would say 20% of the Speedy's that cross my bench have broken mainsprings.

Time for a full service.