The knucklehead is a

retronym A retronym is a newer name for an existing thing that helps differentiate the original form/version from a more recent one. It is thus a word or phrase created to avoid confusion between older and newer types, whereas previously (before there were ...

used by enthusiasts to refer to a

Harley-Davidson Harley-Davidson, Inc. (H-D, or simply Harley) is an American motorcycle manufacturer headquartered in Milwaukee, Wisconsin, United States. Founded in 1903, it is one of two major American motorcycle manufacturers to survive the Great Depressi ...

motorcycle A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...

engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gen ...

, so named because of the distinct shape of the rocker boxes. The engine is a two-cylinder, 45 degree, pushrod actuated

overhead valve An overhead valve (OHV) engine, sometimes called a ''pushrod engine'', is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with earlier flathead engines, where the valves were located be ...

V-twin engine with two valves per cylinder. It was the third basic type of V-Twin engine used by Harley-Davidson, replacing the Flathead-engined VL model in 1936 as HD's top-of-the-line model. The engine was manufactured until 1947 and was replaced by the

Panhead The panhead is an overhead-valve Harley-Davidson motorcycle engine, so nicknamed because the rocker covers resembled cooking pans. The engine is a two-cylinder, two-valve-per-cylinder, pushrod V-twin, made in both 61 c.i. (EL) and 74 c.i. (FL, ...

engine in 1948. The Knucklehead-engined models were originally referred to as "

OHV An overhead valve (OHV) engine, sometimes called a ''pushrod engine'', is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with earlier flathead engines, where the valves were located bel ...

s" by enthusiasts of the time and in Harley's official literature; the nickname arose from the California chopper culture of the late 1960s. As the design of Harley-Davidson engines has evolved through the years, the distinctive shape of the valve covers has allowed Harley enthusiasts to classify an engine simply by looking at the shape of the cover. The knucklehead engine valve covers have contours resembling knuckles on a person's fist that give the knucklehead its name.

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Images of each style of Harley-Davidson engine
{{DEFAULTSORT:Harley-Davidson Knucklehead Engine Knucklehead

See also

References

External links