Piston Question

[acw592]

I just tore the top end down on my 400EX and was wondering if I still had the stock piston/bore? The initials KCY are on the top of the piston as well as all 4 valves so I was guessing these were the stock ones? I figured one of my fellow riders would know, Thanks!

[underpowered]

sounds stock, a wiseco would have like a 10 digit part number stamped in it and a JE is plain.