Why my seiko speedtimer 7015 chronograph run smoothly when its day(morning till evening)
But its stop and heavy when its time to changing the day date,whats the problem and how to fix it..
Absolutely, the hairspring is the most delicate thing in the watch- when it comes to manipulation.
It's unlikely that the hairspring was like that before you removed the balance cock. It simply wouldn't have run. It can't get like that from a drop or even being thrown from a rooftop.
As I understand it, the Chinese movements often leave the factory unlubricated and even with manufacturing debris present. This was probably the cause of stopping.
Got it! I am pretty sure my handling was a major contributor to this. But as I said earlier, the watch had an issue (likely with the hairspring) even before any handling. Could the hairspring really go bust even when the movement is cased? Something doesn't add up to me.