As if we could ever forget him! Imagine how long the stroke was on those engines. More than likley 3000 RPM with major torque. I copied that picture to my collection and my have it made into a tee shirt.
About fifteen years ago I saw someone pedaling around on a motorless Harley bicycle that was basically this bike. I didn't stop them to ask about it though.
this one makes it look like they were trying very hard to not change drastically the look of the bicycle (as opposed to the engine filling the space created by the frame)