Harley-Davidson crummy by design | Joel S Aufrecht Home Page

William Harley created the thumping staccato in 1907 when he opted to graft a second cylinder onto his one-cylinder engine design rather than whip up a true two-cylinder engine. Harley used a connecting rod to join two pistons to a single crankshaft. This, combined with Harley's V-shaped engine design, resulted in a rough rumble caused by pistons that don't fire at even intervals. And so the sound was born.
Spine-rattling vibrations that stress the bike's structure and components were a byproduct of that design choice. Due to all that shaking, rattling and rolling, classic Harleys tend to age rapidly ...