Service Citizen chronograph, calibre 8100

Movement looks to be in good condition.

Watch is running, but not great.

I remove the osculating weight.

The reset lever is situated underneath the chronograph bridge.

Like the Seiko 3169, the citizen 8100 has a clutch on the chronograph wheel.

I take the movement out of the case. Beautiful purple sunburst dial.

I remove the hands and dial and you can see the day/date disks.

Underneath the day disk you can see the day/date mechanism.

Here you can also see the setting/winding mechanism.

I start taking the base movement apart.

Movements sometimes look clean, but once you start taking them apart you find the dirt.

Here you can see the gear train layout.

Old mainspring.

I clean the movement and fit the mainspring back into the barrel after lubricating it.

I fit the cap jewels and see that the balance moves freely.

I put the base movement back together.

I put the resetting mechanism back together.

Base movement and chronograph almost back together.

I put the setting/winding/date/day mechanism back together.

Movement goes back into the case.

I’m happy with the performance.

I find this movement exceptionally well made and a step up from Seiko’s 6139 because it’s thinner, has a fly back mechanism and you can manually wind it. Also I like the 6139!!