hi everyone, todd here.
my apologies in advance, this post is going to be a bit wordy.(long)
i am in the process of reassembling a Waltham sz. 0
after getting the wheel train back in and the bridges in place i tried giving it a little spin with a piece of pegwood and it was smooth as silk.
however, once i tried giving the MS a little wind i have found the train runs for about half a revolution of the centre wheel and stops dead. locked up. i found if i manipulate the fourth wheel it will start up again then stop.
furthermore, i found that if i loosen the two screws holding the bridge of the fourth wheel and escapement wheel a quarter turn each the train starts up.
naturally i suspected a damaged gear tooth but i have examined all under a microscope and have thus far found nothing.
is there another possible cause of this problem?
i am considering removing one wheel at a time starting with the escapement wheel as a possibility of isolating the offending wheel.

Among the various "tricks" in the placement of the ephemera collectively manufactured and emplaced in watches are ASSEMBLY SCREWS that LOOK THE SAME . . . BUT ONE IS TOO LONG!!!!!!

These weapons of ticking destruction when emplaced in the wrong threaded hole can and WILL stop the watch by engaging a rotating part that is supposed to keep rotating.

Oftentimes these little tricks of the evil movement designer are hidden in plain sight holding down wind and set movement retainer plates and somesuch, but rest assured they will stop things and you have to find them and put them in the right place where they came out of for things to start working again.

The other thing (of course) is you might have put in one of the train wheels (usually #3) upside-down.

hi David, i found the problem and it seems to be me.
bottom pivot on the 4th wheel is broken.

it wasn't broken when it came out of the cleaning machine because i inspected everything.
i must have broken it during reassembly.
glad i am only working on scrappers right now.
a lesson learned.
Todd

Lining up the pivots to the plates for final assembly takes infinite patience.