Fixing a stalling Slava 2414 mechanical watch

This is a photo post about repairing a Russian Slava 2414 21-jewel movement with a loose cannon pinion, that causes the hour and minute hands to stall at about 10 pm. I managed to fix the problem without replacing any parts. Just cleaning and turning a gear wheel the opposite way on reassembly fixed the slipping clutch.

Introduction

The watch was bought on a market in Sofia, Bulgaria. It was dirty and with a disgusting strap, but after a bit of cleaning it turned out to be in good shape and not very worn. The winding and ticking seemed healthy.

Unfortunately it had the loose cannon pinion problem that seems to be common with this movement, as discussed in this repair question.

The cannon pinion in a watch is typically associated with a clutch mechanism that has to slip when setting the time with the stem. When not slipping it transfers the rotational force from the movement to the hour and minute hands. The problem here is that the clutch becomes so loose that it can't transfer enough torque to reliably move the hands along. It typically shows when the date mechanism activates, which requires more torque, and indeed that was the case with my watch. At about 10 pm the hour and minute hands would just stop while the seconds keep moving.

Another symptom is that the hands move extremely easily when setting the time.

I have never tried to take apart a mechanical wrist watch before, but with nothing to loose and all to gain I thought it might be fun to take a shot at it. I realised it could turn into a nice hobby with plenty of cheap old russian watches available here in Bulgaria.

Disassembly

Here is the watch:

There is a dedication on the back. It mentions the year 1986 / 87.

The back plate pops off. There is no water seal.

Initially I was confused about how to move on from here. The screws holding the movement could get off and the stem comes off the typical way by pushing a little button, but the movement could never get out through the back because of the watch case design. I asked about the issue in this thread and it turned out that the front of the watch pops off. It's front loader watch:

The tools

The tools I am using come from this kit bought of amazon.co.uk. It is not of very high quality, but I chose it because of the nice box and the big variarity of tools. (Note, the bottle of oil seen in the picture was not included).

The smallest screwdriver was however not small enough to engage with the small screws in the side of the movement that holds the face plate on. I had to file one of the punch tools into a screw driver using a nail file:

The other screwdrivers could use a bit of filing as well. They were not hardened and not very well machined. After some filing, they worked reasonably well, though.

The tiny screw in the side of the movement that releases the face plate:

The repair

Under the face plate we see the date mechanism:

The big retaining plate was removed along with some gears and we can see the cannon pinion:

Here it is attached to a gear wheel which together act as the mentioned clutch. The part was contaminated with oil which may explain the slipping issue:

The gear wheel did not want to come off easily. I had to use a washer to hold it and punch the cannon out:

The disassembled cannon pinion and gear wheel:

The best degreasing agent I had around was the Liqui Moly Air flow sensor cleaner. It is designed to dissolve grease and dirt from the very delicate air flow sensor in a car and to leave absolutely no residue. Beware that I have no real knowledge about watch repair, so don't take this as an endorsement to use this product for cleaning watch parts.

I put the relevant parts in a little glass and gave them a good clean and shake

The cannon pinion and gear could be reassembled with a little tuck. I turned the gear wheel the opposite way, so the part now looks like this:

Reassembly was tricky, as this post also alludes to. But I think I had it easier than the guy in the link, as my movement didn't seem to drop that little part from the retaining plate that kept falling off for him. The part can be seen right between the dates 29 and 30. There is a little spring pushing on it forming a ratcheting mechanism for the date wheel.

To me it was more challenging to put the hands back on aligned correctly and without causing damage

The watch with a black strap ready to wear: