Fok 15 Diesel model airplane engine. First Runs.

I recently acquired this lovely FOK 15 diesel model airplane engine. It was made in Hungary about 1967. It is a 1.5cc displacement engine (or .09 cubic inch). It looks like it was run before but its in extremely nice condition. It takes very little pressure to turn the contra-piston screw. That makes we wonder if the contra-piston has an O-ring seal instead of the more common friction fit. It runs very well and is easy to start. it does like to loosen the prop nut when it fires. I had to re-tighten it several times while making this video.