What is it about the V-Twin engine? Is it the sound, the potato-potato or the syncopated rump-diddle-ump bump bump? Or is it the galloping torque, the thrusting pulses of pounding lunge, and the creamy rush of linear acceleration? 

Venerable V-Twins T.J. Rafferty
Harley’s 1,000cc EL and 1,200cc FL Knuckleheads spanned 12 years of production. Collector values for the 1930s and ’40s models have risen in recent years.

Maybe it is just practical engineering – keeping a narrow vehicle narrow, its function complementing its form. The decision wasn’t too complicated: The bicycle frame is V-shaped, so let’s build an engine to fit the space. Thus was born the first American V-Twin in production, a 1,000cc engine with the cylinders displaced at 50 degrees built by Glenn Curtiss in 1904. 

Venerable V-Twins T.J. Rafferty
The first American V-Twin was probably the 1903 Orient, designed by Charles Metz and built in Waltham, Massachusetts. The 750cc engine was based on the French Aster Single but with an extra cylinder arrayed at a 45-degree angle.

Journalist John L. Stein told us how the arrival of the “safety bicycle” at the turn of the century set the pattern for motorcycling:

“This new-style frame created a perfect V-shaped space between the head stock, the bottom bracket, and the seat post,” he said. “A narrow-angle V-Twin fit perfectly there, morphing the bicycle into the V-Twin motorcycle in one easy, seamless step, with no reinvention of the fundamental contrivance required.” 

Venerable V-Twins T.J. Rafferty
Glenn Curtiss of Hammondsport, New York, produced his first V-Twin in 1904, and this model is from 1909. The 1,000cc en-gine’s cylinders were set at 50 degrees, and a single cam operated the intake and exhaust valves. With 6 hp on tap, the long and lean Curtiss weighed just 160 lb and was good for 60 mph.

Stein said that if you can ride a bicycle, “riding a Harley might be just as easy to comprehend because you already ‘get’ the bicycle. Good, bad, or ugly, that H-D has lasted over a century using this configuration means it works on some fundamental, practical level.”

Venerable V-Twins T.J. Rafferty
The Marsh brothers got started in 1899 and were joined by Charles Metz in 1905 to become Marsh Metz. The company’s 1,087cc 90-degree V-Twin appeared in 1909 and was rated at 10 hp.

It’s the long-legged, galloping torque of the Twin, y’all. Harkenin’ back to our cowboy days.  – Bill Dutcher, former racer and founder of the Americade rally.   

Venerable V-Twins T.J. Rafferty
The Cyclone 1,000cc 45-degree V-Twin was the most powerful engine on the market in 1914. With bevel-drive overhead cams and more than 20 hp on tap, the Cyclone could reach 110 mph.

What’s Your Angle?

The narrow-angle V-Twin was standardized as the American powerplant of choice early on. The V angle varied slightly: Curtiss settled on 50 degrees, the Indian engine was 42, and the Harley was – and remains – 45 degrees in its air-cooled models. So if packaging was the primary consideration, what was the downside in using a long-stroke V-Twin? Vibration.

Related: Glenn H. Curtiss Museum Opens Dawn of a Legacy Exhibition

The 90-degree V-Twin, such as found in Ducati and Moto Guzzi, has perfect primary balance and only minor secondary (twice engine-speed) shakes. The Marsh Metz American Motorcycle Company built a 90-degree V-Twin in 1909, stating in its brochure that “45 degrees, the angle so generally used in motorcycle construction, is the worst possible angle, being always out of reciprocating balance.”

Venerable V-Twins T.J. Rafferty
Indian’s 42-degree big-base 8-valve developed 20-plus hp. Even the standard-base OHV engines were capable of speeds over 100 mph, and they remained in production for nearly a decade.

However, Harley-Davidson endured with the 45-degree inclination, minimizing vibration with knife-and-fork connecting rods, counter-balancers, and rubber-mounting over the years. 

Venerable V-Twins T.J. Rafferty
The consumer market for Harley’s 45-degree 1,000cc 8-valve was limited by its $1,500 price. The 8-valve Indian cost only $350.

Harley motors are big chuggin’ lumps that retain a good measure of the original character. They sound and feel like American tradition carrying on down the road. In cruise mode, the comfort zone between 40 and 70 mph, the big V-Twins play bass and drums. The 4-cylinder sportbikes are more like electric guitars. 

Ah, the good ol’ narrow-angle V-Twin: large, obvious, set in its ways, proud of its lack of sophistication, self-satisfied, lumpy, inclined to brighten itself up with baubles and bangles, firmly resistant to the charms of progress or fresh thinking. If it were human, it’d be Jed Clampett. — Cook Neilson, former journalist/racer.

Venerable V-Twins T.J. Rafferty
The 1938 Crocker 45-degree V-Twin made more power than the Harley Knucklehead and was considerably lighter. Total pro-duction was only about 70 machines.
Venerable V-Twins T.J. Rafferty
The Harley-Davidson Knucklehead made its debut in 1936, with the market’s most muscular-looking engine.

The Sexy Bits

When it comes to shimmy and shake, one person’s vibration may be another’s vibrancy. In a predominately male sport, the reverberation of those staccato firing pulses has been associated with elevated levels of testosterone. 

But that thump isn’t specific to one gender. It is an elemental component of those sensations that rider/writer Melissa Holbrook Pierson calls “the erotics of risk,” and Hunter S. Thompson’s credo, Faster, faster, till the thrill of speed overcomes the fear of death, is tattooed on the arm of a lovely female rider we know.

Venerable V-Twins T.J. Rafferty
In 1954, the venerable Harley K model flathead became the KH, with a longer stroke to make 883cc. The KH was supplanted by the OHV Sportster in 1957.

Certainly, the sexual aspect can be attached to any, uh, robust activity (no pun intended), but motorcycling is an apt metaphor with its attendant noise and excitement. But the psychologizing gets dodgy when the male/female traits are presented in media as prominent aspects of the sport rather than used simply in the realm of titillating trailers for B movies. (Okay, “titillating” was on purpose.)   

Venerable V-Twins T.J. Rafferty
American sport-touring in 1960 was defined by the XLH Sportster. The leaner, meaner XLCH was the original streetfighter.

That said, female riders have been scorned by all manner of male mouthbreathers over the years, including nonriders, who are somehow uneasy about women on motorcycles. These fellows may be jammed up between generalized misogyny, repressing lusty thoughts about their mothers, or just pissed off in general. Or they got passed on the outside by a woman on a Sportster. Fortunately, their numbers seem to be waning. Motorcycling doesn’t discriminate by gender.

In any case, the consensus is established: Sex sells, and fantasy sells even better, so the math isn’t too difficult. 

Rumbling Into the Future

The King of the Baggers and Baggers Racing League have demonstrated the performance capabilities of big V-Twin touring bikes – and illustrated that Harley and Indian consider it a worthy marketing investment. The MotoAmerica series has expanded to 14 races for 2023, and the Hooligan Class continues to showcase the lighter air-cooled V-Twins. 

Related: Tested! King of the Baggers Harley-Davidson Factory Racer

The “American engine” has been around for 120 years, and it shows no sign of fading away. Its development has been, as they say, incremental. Perhaps that accounts in large part for its longevity. That and the primal, sexy rumble.

Venerable V-Twins T.J. Rafferty
The Harley Panhead (1948-1965) was the 1,200cc Hog of popular choice. It’s illustrated here by smilin’ Mike Vils on a 1955 FLE Hydra-Glide rolling down the road and feelin’ grand.

Somewhere on a desert highway, she rides a Harley-
Davidson, her long blonde hair flyin’ in the wind
– Neil Young, songwriter


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