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picked up a 99 kdx 200 a couple months ago and just now getting around to checking out the bike mechanically. the bike runs great starts first or second kick every time and compression is 150. I removed the exhaust and the piston has some scoring on the skirt is this normal or do I need to do a top end and when do you recommend having the cylinder replated.

It is hard to say from reading what you saw. Pictures of a complete tear down would be a lot more helpful.

yup, pic's would be nice. You may have some light scuffing, but I don't think you should have scuffing or scoring such that you could catch your fingernail on it (fella once told me that was the 'rule of thumb'..not sure how golden that advice is though, to be honest)
Since it's new to you, I think it's a good idea to pop it open anyway just to give everything a good inspection. You can replace the rings and needle bearing for sure, inspect and clean cylinder, check lower rod bearing, clean kips, etc.

Thanks for the input. I am planning on pulling the head and carb and sending to RB . I will post some pics when I get her tore down.

here are my tear down pics. looks like I will need a new piston.

It also looks like you may need a new nikasil replate on that cylinder...that is some significant scoring on the "electrofusion" surface of the jug.

Yeah that jug (err elctro-plating) is worn out and I (think) is see a couple small nicks. Give Millennium a call, if you don't buy a piston from them, you'll need to send your new piston kit with the cylinder, so they can be "matched".

yeah there are a couple small nicks in the jug and the piston is trashed im amazed the compression was good the way everything looked!!