Introduction
Harley-Davidson motorcycles have always celebrated their special identity within the motorcycle field, and a lot of this identity has to do with the engines that power the vehicles. The engine is at the core of what makes every Harley a Harley, and these engines have quite an illustrious history that distinguishes them from the engines of other makers.
Early Beginnings
The first Harley-Davidson motorcycle engine weighed in at just under 50 pounds and was a single-cylinder, 24.75-cubic inch, F-head valve configuration affair. Unlike what typical car manufacturers do, Harley-Davidson refreshes their engine very 15 years, so the cycle with these motorcycles is quite different. Originally, Harley-Davidson motorcycles weren't motorcycles in the sense that we understand them at all. They were quite literally a bicycle with a motor more or less attached. As such, as Harley-Davidson machines became more and more complex and more like the machines known today, their weight grew drastically heavier, and as a result the engines and fuel tanks grew gradually larger and meaner to support the vast change in design. Thanks to the advancement in engine size and strength, the motorcycles not only were capable of still running, but they also became more efficient, traveling at longer distances and at quicker speeds.
Past Engines
The engine is at the heart of each Harley-Davidson motorcycle, and there have been quite a number of variations throughout the years. The initial brand of engine was the Flathead engine, manufactured from 1929 until 1974. These engines featured valves that ran along the side of the engine and that opened upward. Its non-complex design was an asset, and the engine cranked out roughly 22 horsepower (rather pathetic by today's standards). Similar to it was the Knucklehead engine, which cranked out an improved 40 to 45 horsepower and was available roughly during the same era. Numerous upgrades to the Flathead and Knucklehead engines have been made available throughout the years. The Shovelhead engine produced 60 horsepower and featured a displacement of 74-cubic inches and was available from 1966 until 1985-it represented a boost in horsepower nearly three times over that of the Flathead. The Harley-Davidson Evolution engine helped take the vehicle into the modern age, with an engine capable of 70 horsepower and a displacement of 81.8 inches. It was produced between 1984 and 1999, and is no longer available.
Current Engines
Moving into the modern day, the Twin Cam 88 engine saw birth in 1999 and provides 80 horsepower and 88-cubic inches of displacement, and represents Harley-Davidson's largest engine. Also, the Revolution engine was introduced in 2001 and is only available on the VSRC motorcycle model, but this engine pumps out an impressive 115 horsepower, while staying relatively small at 69-cubic inches. Unlike so many other engines of the past and unlike the Twin Cam 88, the Revolution is water as opposed to air-cooled, and features four overhead cams.
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