Motorcycle Sounds I Enjoy

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Kevin Cameron has been writing about motorcycles for nearly 50 years, first for <em>Cycle magazine</em> and, since 1992, for <em>Cycle World</em>. (Robert Martin/)

For me, best of all is the sound of a racing motorcycle out on the course, accelerating through the gears. That was intensified during Goodyear’s 1979 pre-Daytona tire test, when Mike Baldwin had to sub for Kenny Roberts (whose factory bike happened to have tight primary gears, making a terminal whine). Accelerating toward turn 2 (the right-hand 180-degree “international horseshoe”), Mike was getting wheelspin that rapidly rose and fell at the chassis weave frequency. “Woo-woo-woo.”

I was able to hear it because hardly anyone else was on the track.

In earlier years, in the quiet of the shop, there was the “tink-tink-tink-tonk” as I slowly turned a wire-spoked wheel, testing each spoke for tension by tapping with the spoke wrench, looking for less-tight spokes.

Ball bearings are fascinating because of their eerie smoothness when new—even when solvent-cleaned. Hold the inner race, give the outer a spin, and enjoy the purity of the motion. But, as a bearing engineer told me years ago, “The processes of failure begin to operate as soon as a bearing goes into service.” I would rebuild pressed-together two-stroke cranks with as many as 50,000 miles, and the most common failures were cage fractures of main ball bearings and con-rod big-end needle rollers whose surfaces were becoming rutted by fatigue damage. Clean up such bearings and spin them (not with air but with a finger) and you could hear the difference from new.

Lots of mechanical equipment today has acoustical monitoring that predicts bearing failure so replacement can be routinely scheduled.

The soft “chunk” sound of the safety-wire pliers as they cut off the twisted 0.032-inch stainless wire after securing a nut or bolt with it. Followed by bending that pigtail in a 180 so you don’t stab a finger on it later.

Early Superbikes (1975–85) made a lot of valve noise during warmup. I liked to picture in my mind the cam lobe, swinging around to take up the clearance, then hurling the valve up off its seat only to be decelerated by the spring for its ride over the nose of the lobe. The sum of all those tiny clearance-clicks made a rushing sound that could be quite loud.

The jingle of the plates of a dry clutch. The bike has just been push-started and the rider or mechanic has stopped to find neutral for warmup. As the clutch lever is held in for this, the plates make that special sound.

Dry clutches made for easier push-starting before 1984, when GP racing switched to running-engine starts. The classic scene (I’ve never been to the Isle of Man) was pairs of riders being flagged off at the start of a TT. In the GPs, it was the whole grid, pushing at once.

In the 1983 process of switching Superbike from 1,000cc down to 750, one detail that was researched was the effect of cam-chain wear on valve timing. Chains are surely better now, but back then there was some change in performance through a race from chain “stretch” (chains don’t stretch—they wear. Ever hear of a frame stretching?). Quick as a wink, here came gear-drive conversions to keep valve timing where it had been so carefully set. Gear drives made a satisfying whine that was quite different from a stock chain. Hearing it was a pleasure.

Gear-driven camshafts make a wonderful whine. (Benelli/)

Race sanctioning bodies love to make rules against such trick stuff. It increases costs! So they require that certain parts be stock—never mind that travel is the “biggie.” Often, stock stuff (such as stock cranks made of material that sets the real rev limit) has to be replaced so often that it costs more than race parts made for the job. Does anyone imagine that stock parts are cheap? Racers regard such arm-chair policy-making as just another kind of weather they must endure in the course of their work.

Which brings me to the brittle crunch that engines make when they “blow up.” While it’s not something I like to hear, it’s unusual enough to deserve a mention. It’s a very brief sound, not really loud, but unmistakable. You see the rider coast onto the grass, lean the bike against something, then start trotting back to the paddock for the spare.

Finally, trail the fingernails of one hand across the cooling fins of the cylinder or head of an air-cooled engine. It’s not really musical but it’s pleasant.

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