Sounding really good Steve.
I used o-ring stock and cut the length I wanted and gel super glued the ends together. Don't know if you know or not but you can get super glue to setup and harden faster if you just breath on it. The moister in your breath I believe does it.
Anyway looks like a really nice engine
Yep, I have seen the method. I just order to size. They make 1/16 o-rings in big diameters for hydro cylinders. 5 for 2 bucks