[Dave at Pelican Parts]

The KS makes me think they are Kolbenschmidt pistons. KS was an OEM supplier for these motors. They're good quality, generally.

The wrist pins come out with some force--they should not just slide out. Br@d had a particular socket extension that was just the right size to use as a mandrel for tapping them out with a hammer. They are, in addition, held in with circlips.

--DD