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Bulova 21J - Citizen/Miyota 82S0 movement Disassembly

sstakoff
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sstakoff WRT Addict

sstakoff

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Sequential disassembly of a 21J Citizen/Miyota 82S0 skeleton automatic movement. Pics only at this time...
I've never worked on one of these before. Seems pretty straightforward although there are a number of differences from a typical swiss automatic. Does anyone know of a service manual for this movement?

The watch is running very fast (+60min/day) with very low amplitude. Removing the balance and pallets I find that the train runs sloppy with minimal wind on the mainspring. Escape wheels runs, then stops and starts several times before the wind is fully released. Nothing obvious on disassembly, but I do see some excess oil has leaked below some of the jewels and is present on the flat side. Perhaps this has attracted some dust or similar. Going to give it a good cleaning and see if that solves the problem - I suspect it will.

More pics here:  https://adobe.ly/2LLB4Jj

DSC_0616-1.thumb.jpg.fcc297b9376389419ae26e2fc279b055.jpg

Edited by sstakoff
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sstakoff WRT Addict

sstakoff

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19 minutes ago, clockboy said:

Looking at your l pics the hairspring does not seem to be sitting correctly on the final bend. This could cause regulation issues.

Thank you - I do agree. Not certain this would create the extremely low amplitude observed. I think that is probably due to a lack of power coming through the train, which is consistent with the action observed with the escapement removed. But, perhaps the hairspring is more to blame. Just don't understand how this would occur suddenly - I assumed the spring was likely in this condition when the movement was manufactured.Will see how the train behaves after cleaning - I haven't had time to put it through the machine yet. I'm also writing this up as a walkthrough (see jdm comment above) - so will repost when that's done.

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