Just noticed on this chart that the bore is 150mm and stroke is listed at 120mm. Another chart lists the stroke at 210mm, which calculates out to 3.7L or 226 cu.in.
Piston speed at 1100 RPM would be equivalent to 1760 RPM with a 5 inch stroke. BUT, if one could govern this speed down to 750 RPM or so, then that would reduce piston speed to Low Speed Status.
This engine has the same Displacement as a 225cu in Slant 6! But only one Cylinder!
Not a lot of info on this engine. I wonder if it has a Counterbalance Shaft?