Following our recent Falloon File about the lovely and talented little Ducati Supermono, Commenter Bob wanted to know: “Why did Bordi use an extra connecting rod instead of the usual balance shafts? BMW had a parallel twin with a third con rod for the same reason. I would be interested in reading a technical analysis of those motors.”
Dear Bob,
Interesting. At first, I guessed Ducati’s Chief Engineer Massimo Bordi probably decided to use a dummy cylinder because he already had a stack of V-twin engine cases lying around, but that idea is quickly out the window when you remember the super lightweight Supermono in fact got its own cases, made from magnesium even.
For background, the limiting factor for most single-cylinder engines is rpm; one big piston rising and falling by itself is (was) hard to balance past 6000 rpm or so, which means debilitating vibration coursing through bike and rider just before something breaks. The easy solution of course, is more and smaller pistons. But for some reason, Sound of Singles got to be a really competitive series around about the late ‘80s, and Ducati wanted in.