Like the original Big Twin—the EL of 1936—the new engines have a single four-lobe camshaft in place of the Twin Cam’s pair. Drive is by chain with automatic hydraulic tensioner. Fewer parts mean reduced noise and lower friction. What was said when the Evo engine first appeared still applies: “We’re killing the noise so we can keep the music.” The EPA sets a maximum sound level, measured in a specified way. Radiated sound is partly exhaust rumble (good) and partly mechanical. Mechanical noises often include energetic high frequencies (clicking, gear whine, etc.), so identifying and suppressing them allows that energy to go into a “richer exhaust note.” Years ago, when Big Twin cams were gear-driven, noise could be generated by excessive backlash (loud clicking from the constant rapid reversals of cam torque) or by tooth form irregularities. Both were expensive to control. Swiss gear-grinding machines were imported to achieve accurate tooth profiles, and time-consuming selective fitting was necessary to control backlash. An automatically tensioned chain eliminates backlash and spreads loads over many sprocket teeth, making operation quiet. We love the precision and beauty of gears, but we also love simplicity.