Early Ferrari and MV Agusta engines were said to have "a sound like ripping canvas." That's a tough one to imagine today in our ripstop nylon world. I imagine that on sailing ships of old when a huge mainsail gave way and the canvas burst in a massive edge-to-edge tear it must have sounded like doom and calamity coming right at you. John Surtees on the Moto Guzzi V8, with it's skinny tires, wistful brakes, vicious handling, and dustbin fairing, must have felt and and sounded the same way as the bike and rider fought their way around the guardrail and tree lined grand prix tracks of 1957. Doom and calamity and sound aimed right at you.
The best sounds today come from v-twin engines. Our Italian friends have not forgotten how to build soul into a bike and into an engine and I have no doubt that exhaust note is an important criteria in determining the final tuning and function of an Italian v-twin. Even the modern MV Agusta four cylinder engine has a distinctly throaty Italian GP sound, no doubt tuned with every intent NOT to sound like a Japanese four.
My Aprilia Caponord has Remus pipes on it and they are much louder and authoritative than the stock Aprilia cans. They are really out of character for "a big trailie" as the Brits call adventure touring bikes. I should take the Remus cans off and return the bike to stock but every time I dive into a turn, blip the throttle for a downshift, and really hear the 60 degree v-twin I get a little farther away from actually going back to the civilized stock exhaust.
Vintagebike.co.uk has a website devoted to, you guessed it, vintage bikes. In the "Sounds" section of the website is a wonderful treasure: Sound clips from great racing bikes going all the back to the 1949 Norton ES2 and 1957 Gilera Four. There are a smattering of modern machines too like the Honda Fireblade and BMW R1150GS so it's a fine opportunity to listen to "then and now" in the racing and motorcycle world. Compare the sound of '49 Norton to the 1150GS and the GS sounds pretty darned nice. Compare the Moto Guzzi V8 or 1967 MV Agusta to almost anything since and you realize that motorcycle sounds may have reached their zenith over thirty years ago. Listen to the sound of the Harley Sportster and you are reminded that it's time to mow the lawn. Yeah, that last comment was a cheap shot but I couldn't resist.
Mike Hailwood on the 1967 MV Agusta is the best sound on the Vintagebike page, better than anything running the tracks today. Modern MotoGP bikes sound too much like modern F1 cars and who wants their bike to sound like a car? The 1957 Moto Guzzi V8 (a 500cc 4-stroke V8 for you newer guys) comes closest to sounding like a modern machine. In 1957 it must have sounded to race fans like something from another planet.
Imagine the times the bike raced in, the black leather suits without advertising, cork lined pudding bowl helmets, split lens goggles, 19 inch racing tires on rain slick tracks. Imagine tree lined and walled streets of the Isle of Man or the long course at Nurburgring. No computer tuning, no video feeds from the bike, just a hugely talented and brave rider astride a machine designed by men using slide rules and a passion for bikes and speed as their primary tools. Put some racing castor oil in a pan on the stove and get it hot until the odor prevades the room if you want the full effect.