Thanks for that link.
A marine version and hear it does idle very slow.
Most 2 stroke cycle engines have a much higher idle speed.
I did see another book on Google Books see this at page 16 near the bottom 1/3 of the page.
Now on page 16 see the area where it mentions of the rate of burn speed by the changing of turbulence in the cylinder by changing the diameter of the tube between then two cylinders. The more turbulence it was said made faster burn. A compromise between fast and slow burn got a quiet engine with good fuel usage. Maybe this is how I can hear the difference between a normal 2 stroke engine and this type where it can idle very slow.
One more Youtube video of one of these engines in a boat.