Twin Peaks

Twin peaks

UP FRONT

David Edwards

TO SOME. IT IS THE PERFECT MOTORCYcle engine. To others, it’s a dusty, musty relic awaiting the scrap heap.

I'm referring to the air-cooled, twin-cylinder powerplant equipped with a solitary intake valve and an equally lonely exhaust valve atop each combustion chamber.

Any number of people will cite you chapter and verse on the reasons that this anachronism should be put to sleep, how liquid-cooling makes for more durable engines, why fourvalve-per-cylinder technology is the only way to go if you’re after combustion-chamber efficiency, how multiple cylinders mean more horsepower. I believe them all, really I do. And just because I’ve got a 1954 BSA Gold Star and a 1946 Velocette, please don’t think that my allegiances reside with those who espouse that the Good Old Days were all good. In fact, ask me what my favorite motorcycle engine is, and I’ll tell you that Honda’s liquid-cooled, 16-valve, gear-cam-drive V-Four, as fitted to the VFR750F and the RC30, may be the most ideal combination of power, feel and exhaust note that's ever been bolted between frame tubes.

Yet, over the past six weeks. I've had the pleasure of keeping company with a trio of air-cooled, two-valveper-pot Twins—our I200cc Project Harley Sportster, a BMW R100GS test bike and this month’s coverbike, a Ducati 900SS (which, sticklers will note, is air-¿/w/-oil-cooled, courtesy of its oil radiator). If these three machines are any indication, there’s some life left yet in the old-style Twin. Reminds me of the cable that Mark Twain sent from London to the Associated Press in 1897 after rumors had been circulated of the great writer’s untimely demise. “The reports of my death.” Twain said, “are greatly exaggerated.”

Certainly, that's the case at HarleyDavidson, where the Sportster and Big Twin can trace their roots all the way back to 1909. the year in which William Harley and the Davidson boys decided that two cylinders arranged in a vee would work pretty well and not take up much more room than the Single the company already had mounted in its bicycle-like frames. Today, 82 years later, while many far-more-advanced machines languish in dealers’ showrooms, Harley sells all the outmoded V-Twins that its assembly lines can churn out, and owns 60 percent of the 850ccand-above market segment in the USA. Not bad for bikes propelled by engines supposedly at Death’s door.

BMW doesn't sell as many bikes here as Harley, and its flagship K1 hasjust about the most up-to-date engine on the road today, what with four cylinders in a lay-down configuration, 16-valves, double overhead cams, liquid-cooling and fuel injection. But it’s the lowly air-cooled, opposed-Twin—a.k.a. the Boxer-Twin— that still holds the hearts of many Beemophiles, as it hals since its 1923 introduction.

Indeed, when in the mid-’80s, the company looked to be phasing out the R-series Twins, the outcry from the faithful was loud enough that BMW revitalized the line, which now has three entries—the R1 OORT tourer, the RI00 standard and the delightfully quirky R100GS dual-purpose bike, the 1991 version of which has captivated everyone on CIT’s staff, dirt rider to roadracer alike.

But it’s the Ducati that really shows how good a simple Twin can be. The 900SS's motor is sweet-running and torquey, sure, but it only pumps out a claimed 84 horsepower, easily 40 down on some big-bore inline-Fours. Yet, because its compact, 904cc engine can be ensconsed in a minimalist frame, and because it doesn’t need a large radiator, a waterpump or a tangle of hoses, the 900 is light.

How light? Well, the bike is 50 pounds lighter than a Bimota Dieci, 92 pounds lighter than a Yamaha FZR1000 and 156 pounds lighter than a Yamaha FJ1200. That lightness, allied with punchy midrange power, means that the Ducati yanks itself out of corners and has better top-gear roll-on performance than a Honda CBR 1000. More importantly, though, it means that the 900SS is an absolute blast to ride.

In fact, that's another common denominator between the three Twins I’ve mentioned: fun. It’s no coincidence that Harley, BMW and Ducati owners are among the most brand-loyal, most enthusiastic riders in all of motorcycling.

But, sad to say, the handwriting is on the wall for the air-cooled, conventionally carbureted, two-valve Twin. A fouror five-valve design’s more thorough fuel burn not only means more power, but fewer pollutants going into the atmosphere. A liquid-cooled engine not only maintains more constant operating temperatures, but its water jackets deaden the clatter that would normally get past to assault ears and noise meters. And fuel injection, more costly and more complicated than carbs, is much more pleasing to the inspectors at the EPA. Looked at clinically, old-style Twins are noisy, “dirty” engines, and as the year 2000 approaches and environmental concerns come to the fore, it may be those inherent characteristics that put the final knot in the noose around the lovable old engine's neck.

Until that time comes, though, the old-fashioned, air-cooled Twin is still with us. My advice is to enjoy it while you can. No, it is not the perfect motorcycle engine, but it's not ready for the scrap heap just yet, either. IS