I have a Korean made 31 day clock that I have had for a number of years. Since it was new, when wound it might run either slow, or fast. Somewhere between winds, I will get it set, and it will keep good time. The next time I wind it it will either gain, or lose time. Any ideas?

How much is it gaining or losing? It could be reacting to changes in temperature, or power differences when the spring is fully wound vs partially wound.

Tom,
I have never given it any kind of a test, but I would say in a week it will gain or loose maybe 6 or 7 minutes.

Donald, to add a touch to Tom's suggestions, If losing Or gaining after rewinding, it could be the mainspring binding to various degrees following each rewind depending upon how it coils up - I'm assuming it is a 'springer', does it have an open or closed spring?

When was it last cleaned and oiled? it could even be the train binding up caused by worn pivots / holes!

Best regards
John Woolsey

John,
I really don't know what type mainspring it has, but I bought it new probably 15 years ago. It has never been cleaned and oiled, but has had the same problem since it was new. It is beautiful, but it is still just a modern Korean made thing. Before I would sink a bunch of money in it, I would probably just buy another clock.

Most of these Korean clocks need attention right out of the box. Most won't go 31 days as advertised without a good clean and oil first.

A word of caution about recently made Korean and Japanese clocks. All metals used in their manufacture are substantially thinner than what most of us are used to. Two critical parts in these clocks that are inferior are the clicks and click return springs. Usually the click wobbles on the mounting rivet, out of the box. Inevitably, the click assembly will fail. When (when, not if) this fails, it happens when the clock is being wound. As the power from the main spring is released in a nanosecond, the winding key will spin wildly, usually taking hide off of the hand winding the clock. By the time the bleeding has started, the whole process has usually bent the second arbor in the clock and/or torn teeth from the main wheel. All of the loose flying metal can become shrapnel.
Yes, please buy a different clock. This next time buy one not made in Korea or Japan. You are very fortunate to have made it 15 years without some catastrophe.
Best Regards,
Dick Feldman