Harley Davidson Knucklehead (1943)
MODEL FL 74
The 1943 Harley-Davidson Knucklehead Model FL 74 is an exceptionally rare motorcycle that was produced during the height of World War II. As the 74 cubic-inch big twin variant of Harley’s iconic overhead-valve engine (introduced in 1936 and nicknamed for its distinctive rocker-box shape), the FL was offered starting in 1941 to meet demands for more power. It featured larger crankpins, heavier flywheels, redesigned rocker arms for improved lubrication, new crankcases without baffles to reduce excessive pressure, larger intake ports, a redesigned manifold, and a new carburetor.
With a 3.43 x 3.5-inch bore and stroke producing 73.73 cubic inches (advertised as 74) and 48 horsepower, civilian production was severely restricted by wartime material shortages. Only 12 F and FL models were built in 1943, down dramatically from 4,069 EL and ES units in 1940. These bikes retained classic details like the “Cat’s Eye” speedometer console and chrome tank accents, making surviving examples prized symbols of American engineering resilience and pre-war performance heritage.
The 1943 Harley-Davidson Knucklehead Model FL 74 is an exceptionally rare motorcycle that was produced during the height of World War II. As the 74 cubic-inch big twin variant of Harley’s iconic overhead-valve engine (introduced in 1936 and nicknamed for its distinctive rocker-box shape), the FL was offered starting in 1941 to meet demands for more power. It featured larger crankpins, heavier flywheels, redesigned rocker arms for improved lubrication, new crankcases without baffles to reduce excessive pressure, larger intake ports, a redesigned manifold, and a new carburetor.
With a 3.43 x 3.5-inch bore and stroke producing 73.73 cubic inches (advertised as 74) and 48 horsepower, civilian production was severely restricted by wartime material shortages. Only 12 F and FL models were built in 1943, down dramatically from 4,069 EL and ES units in 1940. These bikes retained classic details like the “Cat’s Eye” speedometer console and chrome tank accents, making surviving examples prized symbols of American engineering resilience and pre-war performance heritage.
Restored with the Highest Quality Workmanship
With the call for more power, a 74 cubic-inch version (the FL) was offered starting in 1941. The “Knucklehead” 74 got new larger crankpins increased in diameter, heavier flywheels, and redesigned rocker arms to improve top end lubrication. The new crankcases for the 61ci and the 74ci OHV engines didn't have the baffles the previous models had to equalize the lubrication to the cylinders, solving some of the problems with excessive crankcase pressure, which helped to produce more horsepower. The "Cat's Eye" design stayed as the speedometer console design, with a chrome band serving as part of the tank and logo design on both sides of the fuel tank. Larger intake ports, a redesigned manifold and a new carburetor also helped to increase its horsepower. With consumers requesting more power, it was derived from a 3.43 x 3.5-inch bore and stroke, equaling 73.73 cubic-inches (advertised as 74 cubic-inches). With the outbreak of WWII, civilian production was limited, and manufacturing materials for anything but the war effort were as well. In 1940, EL and ES production totaled 4,069 units. By 1943, it had fallen to only 158 EL and ES bikes, and only 12 of the F and FL bikes.
FL STATISTICS & FEATURES: Engine: 73.73ci air-cooled OHV 45-degree V-twin, 48hp. Black leather seat, and new Shinko 5.00-16 tires mounted on black painted wire wheels. Chrome accents include headlight, horn, air cleaner, tank badge, side stripes, tool box, and speedometer case.
FL STATISTICS & FEATURES: Engine: 73.73ci air-cooled OHV 45-degree V-twin, 48hp. Black leather seat, and new Shinko 5.00-16 tires mounted on black painted wire wheels. Chrome accents include headlight, horn, air cleaner, tank badge, side stripes, tool box, and speedometer case.
