Z1OwnersClub GB

Hi peeps could you please help not sure how it should look take the spark plug out of my 1976 z900 A4 and the top of the piston is a bit damp should it look like that or should it be bone dry runs fine apart from firing on three for a little while then fine. thanks for your help

Could be a leaking valve stem seal causing it to run on 3 until warmed up.
The dampness would be oil assuming that's the same cylinder that is slow to fire.

thank you will check