Bought a "non-functioning" cuckoo clock off ebay a few weeks ago. Using my superb skills (basically fiddled about with it for hours), I managed not to totally ruin it but - actually got it working?
The clock mechanism itself, well no way was I going to fiddle with that but that worked anyway. The chiming and cuckooing parts didn't work. The worst bit was threading the chains around the drive wheels.
Just a closing thought, the cuckoo clock is a jokey thing but in fact it's a damn clever bit of mechanics imho. On the hour and 1/2 hour a little door opens a wooden cuckoo pops out, opens it's beak and waggles it's tongue in time to the cuckoo-bellows sound and rounds off with a nice hammered chime sound, cuckoo retreats inside and door closes. All done with bits of wood cloth and wire - and no spring power in sight.
Harry Lime underestimated the cuckoo clock :-) {Cue Zither music}... dang de-dang de dang,,,,, de-dang.....)
Happy Christmas.