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Kdx 220, first time top end rebuild, replate. Made a rookie mistake, didn’t wash cylinder, my bad. After 30 minutes took back apart, found this. The only scratch I feel with finger nail is the one below the intake port, the others I see but don’t feel. Just spent hundreds, really hate to spend more, thoughts?

where's the piston ring gap?

.25mm, set by Millenium. Also, I didn’t think about it at the time, but it was pretty cold outside, I had a 140mj in the stock carb, the plug showed too lean. Tried to save some money doing this myself, followed the service manual, live & learn.

Sorry. I meant, where like 1:00 or 5:00 (360 degree rotation)

Why did you take it back apart? Did you just remember about washing it or did something else happen?

Can you post a few pictures of the piston?

What was your warm-up technique (break-in) when you cranked it?

Top ring, 7- o’clock, bottom ring 5-0’clock. I had the pipe off, looked inside, could see scuffs so took it apart. Don’t have piston pics, and now it’s back together. Waiting to start it till I get some feedback. I did some heat cycles, followed the Wiseco website recommendations, which is very gradual.

If the ring and piston pin locations are away from the scratch, I would just run it. It's not like a deep gouge is it?

Break in sounds good to me. I was wondering about four corner seizure or wear due to revving high on a cold start / improper break-in.

Not deep at all, barely feel it, I’ll just run it, thanks!

From what you are describing, I would just run it. You are not trying to put a man on the moon with that engine. :-)

Sorry. Could not see what’s wrong. Hope it all goes good!