99 kx250 ring size - numbers on piston?

[876mx]

I took the cylinder off of my KX today to replace the rings. The man I bought it from didn't remember what size he installed but mentioned there would be several numbers on the top of the piston that tells what size it is.

The numbers were barely visable, and there were two, plus the letters "CD" below the two numbers. The top # reads O0016, and the one below it reads 617M0C640.

So, what size rings do I need to order?

[kx666]

is this a stock piston or after market?

[don46]

You have a wiesco piston, the number on the piston should be 617mo6640, this is a standard bore piston that fits from 92-01 the replacement wiesco ring part # is 2614cd. The last for digits are the bore size 66.40 mm

[gowen]

STD Bore, but make sure you get them from Wiseco. You can get them directly from http://www.wiseco.com or http://www.denniskirk.com