"The Gold Wing is the flat cylinder design," Aoki insists. After testing the signature, horizontally opposed layout in four-, six- and eight-cylinder denominations, the six won going away. Juggling incompatible dynamics such as exhaust emissions, noise, weight, fuel mileage, horsepower, torque and driveability made finding the magic engine size difficult. Testing on American roads, Aoki's team started with a 1657cc mutation of the existing 1520cc six. After dissecting everything from the current 1500 to a two-liter beast, input from American riders on American roads finally set the 2001 six's displacement at 1832cc. And because the new engine would be a stressed chassis member (no rubber mounts to squelch vibration), attaining Gold Wing smoothness meant moving beyond the flat six's theoretically perfect primary and secondary balance factors. For starters, that meant scrutinizing the balance factor of any engine bit that spins to cut high-load harmonic tremors.