Harley-Davidson Motorcycles replaced its K model flathead motorcycle with the Harley Sportster in 1957. The Sportster owes its existence to the K series models, since it adopted many of its features. However, the Sportster differed from the K series as a lighter, narrower bike to compete against the influx of Norton, Triumph and BSA motorcycles from England. The Sportster remains in production as of 2012 and is the longest running motorcycle model produced.
Harley-Davidson enjoyed immense popularity before World War II and the immediate postwar years, but eventually the lighter, faster and cheaper British bikes carved a niche in the North American motorcycle market. The answer from Harley-Davidson was the Sportster, which enthusiasts consider the first muscle bike. The Sportster derived from the Harley K series bikes produced from 1952 to 1956. The KH and KHK models featured an 883 cc side-valve engine with aluminum head and cylinders, and the V-twin design with two cylinders and two valves per cylinder. The Sportster kept the K series’ frame, the engine case, suspension and brake system, and the right foot shift. However, the Sportster used an overhead valve 883 cc engine with iron cylinders and heads.
1950s and 1960s Models
Harley-Davidson expanded its line of Sportsters to include a dozen different models. In 1958, the motorcycle maker introduced the XLCH, a stripped-down, lighter version of the standard XL and XLH. The XLCH featured a peanut-shaped fuel tank, staggered dual exhausts, larger valves and ports and magneto ignition. In 1959, Harley introduced a nacelle headlamp on the Sportster XLH and valanced front fender. It could cover the quarter-mile in 14.5 seconds at 90 mph. The Sportster XLR arrived in 1962 for track racing, and an all-aluminum front brake drum appeared in 1964. The following year saw the XLH and XLCH models upgraded to a 12-volt electrical system. By 1967, Harley began phasing out the kick-start for electric ignition on some models. In 1979, Harley abandoned the kick-starter altogether.
1970s and 1980s Models
The Sportster’s Ironhead engine received a modest makeover in 1972 with its engine displacement enlarged to 1000 cc. Harley replaced a steel connection node to the rear of the frame under the seat with a U-shaped steel strip, but the connection could not handle the stress. Harley recalled 1972 models to weld reinforcement strips to strengthen the connection between the rear fender strut and rear shock with the frame. For 1974, Harley moved its right foot shift to the left to comply with new mandates from the U.S. Department of Transportation. In 1986, the maker dropped the Ironhead for the 1100 cc Evolution, or Evo, engine that provided a smoother ride with less engine vibration.
In 1990, Harley-Davidson expanded its paint options for the Sportster and added a 40 mm constant velocity Keihin carburetor with an accelerator pump. A five-speed transmission replaced the four-speed in 1991, and belt drive replaced chain drive on the 883 Deluxe and 1200 Sportsters. All Sportsters received belt drive starting in 1993. From 2000 on, the Sportster remained essentially unchanged except for minor styling modifications using bullet-style turn signals and restyled mirrors. In 2004, the engine became rubber-mounted.