Hi Sandblaster
Thanks for advices. You are right, forks are from 1990 or 1991 kx 250 (thats what previous owner told me).
As far as I know, I have a 1990 version, friend checked by VIN numer, and piston from this year was a perfect fit.
I've found out, that power valves are the same for 90 and 91.
Here are some bits which I need to buy:
12005-1145
12005-1153
13236-1250
Still have no idea, how does last part connects with governor shaft
and what makes power valves to set back to start position, when RPM goes down. I know, that governor shaft goes back, but how does this affects lever and vales I don't know yet
Here are some more pictures from my work