1956 Harley-Davidson FL

Nicknamed for the shape of its distinctive cake-pan valve covers, the Panhead engine was introduced in 1947, addressing the previous Flathead's overheating issues with an overhead valve design and switching from cast-iron to aluminum cylinders. It would go on to become one of most recognizable motorcycle engines ever, assuming the title of The Motor Company's flagship powerplant for almost two decades.

• Engine: 74ci (1,208cc) air-cooled OHV 45-degree V-twin, 3-7/16in x 3-31/32in bore and stroke, 7.5:1 compression ratio, 55hp @ 4,800rpm
• Top speed: 100mph (est.)
• Chassis: Dual downtube steel cradle/59.5in (1,511mm)
• Brakes: 8in (203mm) drum front and rear
• Weight: 612lb (277.6kg)
• Fuel capacity: 3.75 gallons gas, 1 gallon oil