World War II
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One of only two American cycle manufacturers to survive the Great Depression, Harley-Davidson again produced large numbers of motorcycles for the US Army in World War II and resumed civilian production afterwards, producing a range of large V-twin motorcycles that were successful both on racetracks and for private buyers.
Harley-Davidson, on the eve of World War II, was already supplying the Army with a military-specific version of its 45 cubic inches (740 cc) WL line, called the WLA. The A in this case stood for "Army". Upon the outbreak of war, the company, along with most other manufacturing enterprises, shifted to war work.
More than 90,000 military motorcycles, mostly WLA's and WLC's (the Canadian version) were produced, many to be provided to allies. Harley-Davidson received two Army-Navy ‘E’ Awards, one in 1943 and the other in 1945, which were awarded for Excellence in Production.
Shipments to the Soviet Union under the Lend-Lease program numbered at least 30,000.The WLAs produced during all four years of war production generally have 1942 serial numbers. Production of the WLA stopped at the end of World War II, but was resumed from 1950 to 1952 for use in the Korean War.
Harley produced the WLC for the Canadian military.
The U.S. Army also asked Harley-Davidson to produce a new motorcycle with many of the features of BMW's side-valve and shaft-driven R71. Harley largely copied the BMW engine and drive train and produced the shaft-driven 750 cc 1942 Harley-Davidson XA. This shared no dimensions, no parts and no design concepts (except side valves) with any prior Harley-Davidson engine. Due to the superior cooling of the flat-twin engine with the cylinders across the frame, Harley's XA cylinder heads ran 100 °F (56 °C) cooler than its V-twins. The XA never entered full production: the motorcycle by that time had been eclipsed by the Jeep as the Army's general purpose vehicle, and the WLA already in production—was sufficient for its limited police, escort, and courier roles. Only 1,000 were made and the XA never went into full production. It remains the only shaft-driven Harley-Davidson ever made.
Harley-Davidson flathead engine
Model W singles, and 45s (DL, RL, and WL)
The flathead engine saw service in Harley-Davidson motorcycles beginning with the Model W's flat-twin, produced from 1919 to 1923, and continuing in 1924 with single-cylinder export-model 21-cubic-inch (340 cc) and 30.5-cubic-inch (500 cc) singles and continued in Servi-Cars until 1973. In the domestic U.S. market, the 45-cubic-inch (740 cc) DL model (1929 to 1931) and its technical descendant, the RL model (1932 to 1936), started Harley's side-valve tradition in the 45-cubic-inch displacement class. The DL and RL models featured a total-loss oiling system and were succeeded in 1937 by the WL 45, which had recirculating oil lubrication. The WL went on to serve in World War II as the U.S. and Canadian Army's primary two-wheeled mount and subsequently as a civilian middleweight through 1952. The engine continued virtually unchanged with various G-based designations in the three-wheeled "Servi-Car" until production ceased in 1973.
The knucklehead is a retronym used by enthusiasts to refer to a Harley-Davidson motorcycle engine, so named because of the distinct shape of the rocker boxes. The engine is a two cylinder, 45 degree, pushrod actuated overhead valve 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 engine in 1948.
The Knucklehead-engined models were originally referred to as "OHVs" 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.
The Panhead was a Harley-Davidson motorcycle engine, so nicknamed because of the distinct shape of the rocker covers. The engine is a two-cylinder, two-valve-per-cylinder,pushrod V-twin. The engine replaced the Knucklehead engine in 1948 and was manufactured until 1965 when it was replaced by the Shovelhead.
As the design of Harley-Davidson engines 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 covers, and the panhead has covers resembling an upside-down pan.
The "Captain America" chopper used by Peter Fonda in the movie Easy Rider (1969) had a panhead engine, as did the "Billy Bike" ridden by Dennis Hopper's character.
Currently, a number of third-party engine manufacturers produce custom panhead-style engines in a variety of bores, many much larger than the original-design displacements. Each manufacturer includes significant subtle upgrades to the original design to drastically improve the performance and reliability while still providing the original styling and overall engine structure.
To be continued... vroom