Let's face it, the sound of a properly tuned exhaust, at least for most americans is part of the soul of your machine. Some manufacturers get it, some don't. What are the best (or worst) sounding exhaust notes you've heard? There are no wrong answers, since this is about opinions.
Personal favorites: Yamaha Vmax and Royal Star-amazing when properly uncorked. Almost sounds like a hopped up small block chevy running around a racetrack. As intense as a motorcycle has a right to be.
Ducatis, pick one, an unabashed staccato howl that makes you understand the romantic involvement that Italians have with there machinery.
British Twins, particularly 270° cranks. Quirky, off beat, both in your face and subtle at the same time. Much like Monty Python, some people understand and appreciate it, others scratch there head.
The worst ones: Honda VFR interceptors. amazing that yamaha and honda can both create a V-4 with such dramatically different souls. The interceptor sounds as hollow and flat as the Vmax sounds nasty. A total let down.
BMW Boxers- Typical Teutonic efficency and engineering (form follows function etc.) The machines are wonderfully designed and utterly soulless with regards to exhaust note. To find the passion and soul of Germany, look to their Brewmasters
