It was an interesting project to build and not all that difficult as models go. All machined from solid stock, except for the flywheel which is a casting.
During the process a demand regulator was constructed so it could be run on propane rather than gasoline.
I even built my own spark plugs to use in it.
Finally it was completed. It did not have much compression. Cranking it with an electric drill, it would pop a little, but simply would not keep running by it's self. Disappointed, I set it aside for a while and built several other projects. But I was bothered by the fact that it had little compression and would not run. I assumed the valves were leaking, so a few days ago I took it apart and re lapped the valves with a polishing compound. Still no compression. But when I removed the spark plug and put a finger over the hole, lots of compression. A little more investigation revealed that the packing nut holding the insulator in was hardly finger tight. After getting that sealed up tight, it runs like--- well an old hit and miss engine ought to run. Take a look at the video and see for yourself.