The Sportster is a line of motorcycles produced continuously since 1957 by the Harley-Davidson Motor Company. Sportster models are designated in Harley-Davidson's product code by beginning with "XL". In 1952, the predecessors to the Sportster, the Model K Sport and Sport Solo motorcycles, were introduced. These models K, KK, KH, and KHK of 1952 to 1956 had a flat head engine, whereas the later XL Sportster models use an overhead valve engine.
Construction
Sportster motorcycles are powered by 45 degree V-twin engines in which both connecting rods, of the "fork and blade" or "knife & fork" design, share a common crank pin. The original Sportster engine was the Ironhead engine, which was replaced with the Evolution engine in 1986. Sportster engines, the 45" R, D, G & W Models 1929 side-valve motors, and the 'Big Twin' side-valve motors, which were: the flathead 74 cubic-inch (1213 cc) Models V , VL etc. (1930–1936), Models U and UL (1937–1948), and the 80 cubic-inch (1,311 cc) Models VH and VLH (1935–1936), Models UH and ULH (1937–1941) have four separate cams, sporting one lobe per cam.
Sportster motorcycles are powered by 45 degree V-twin engines in which both connecting rods, of the "fork and blade" or "knife & fork" design, share a common crank pin. The original Sportster engine was the Ironhead engine, which was replaced with the Evolution engine in 1986. Sportster engines, the 45" R, D, G & W Models 1929 side-valve motors, and the 'Big Twin' side-valve motors, which were: the flathead 74 cubic-inch (1213 cc) Models V , VL etc. (1930–1936), Models U and UL (1937–1948), and the 80 cubic-inch (1,311 cc) Models VH and VLH (1935–1936), Models UH and ULH (1937–1941) have four separate cams, sporting one lobe per cam.
The cam followers used in Sportster engines, K models, big twin side valve models, and the side-valve W Model series were a slightly shorter version of the followers used in the larger motors, but with the same 0.731 in (18.6 mm) diameter body and 0.855 in (21.7 mm) diameter roller follower since 1929. The company used similar cam followers for decades with minor changes, from the 1929 to the Eighties.
Sportster engines retained the K/KH design crankcase design, in which the transmission is contained in the same casting as the engine, and driven by the engine with a triple-row #35 chain primary drive and a multi-plate cable-operated clutch. Models since 1991 have five speeds; 1990 and earlier models had four speeds.
The engine was mounted directly to the frame from 1957 through the 2003 model year. While this system allows the bike to be somewhat lighter with more precise handling, it also transmits engine vibration directly to the rider. Sportsters released in 2004 and later use rubber isolation mounts and tie links to limit engine movement to a single plane, which greatly reduces vibration felt by the rider. Buell motorcycles built with variants of the Sportster engine have used a rubber mount system since 1987.
The Model K, from which the Sportster evolved, was the first civilian motorcycle produced by Harley-Davidson with hydraulic shock absorbers on both wheels. Common usage calls this a K Model.
Sportster engines retained the K/KH design crankcase design, in which the transmission is contained in the same casting as the engine, and driven by the engine with a triple-row #35 chain primary drive and a multi-plate cable-operated clutch. Models since 1991 have five speeds; 1990 and earlier models had four speeds.
The engine was mounted directly to the frame from 1957 through the 2003 model year. While this system allows the bike to be somewhat lighter with more precise handling, it also transmits engine vibration directly to the rider. Sportsters released in 2004 and later use rubber isolation mounts and tie links to limit engine movement to a single plane, which greatly reduces vibration felt by the rider. Buell motorcycles built with variants of the Sportster engine have used a rubber mount system since 1987.
The Model K, from which the Sportster evolved, was the first civilian motorcycle produced by Harley-Davidson with hydraulic shock absorbers on both wheels. Common usage calls this a K Model.
Model K series
This is developed from the earlier 45 W model, but with the revised flat head engine and new 4-speed transmission contained in the same castings as would become the Sportster. The connecting rods would be inherited by the Sportster along with many other design features and dimensions.
* Model K and KK 1952–1953: 750 cc side-valve engines, using the 45 model bore and stroke
* Model KR (racing only) 1953–1969: 750 cc side-valve engines
* Model KH and KHK 1954–1956: 885 cc side-valve engines, using the 45 model bore, but with the stroke increased to 4.5625" (115.89 mm). This is the only small twin with a longer stroke than 3.8125", which is otherwise universal to the entire 45/K/Sportster line from 1929 to the present (exception: XR750, XB9 Buell).
X series Sportsters
* XL, Ironhead, 1957–1985: 900 cc (883 cc actual) and 1,000 cc Ironhead overhead-valve engines with cast iron heads
* XR750 (racing only) 1970–1971: 750 cc overhead-valve engines, iron heads
* XR750 (racing only) 1972–1985: 750 cc overhead-valve engines, alloy heads
* XLCR Sportster (cafe racer)1977–1978: 1,000 cc overhead-valve engines, iron heads
* XR1000 (racing only) 1983–1984: 1,000 cc street model using XR racing cylinder head and other XR engine parts.
* XLR (racing only): 883 cc overhead-valve engines, iron heads
* XL, Evolution (also known as the "Evo"), since 1986: 883 cc, 1,100 cc and 1,200 cc Evolution overhead-valve engine, alloy heads
Source : en.wikipedia.org/wiki/Harley-Davidson_Sportster
This is developed from the earlier 45 W model, but with the revised flat head engine and new 4-speed transmission contained in the same castings as would become the Sportster. The connecting rods would be inherited by the Sportster along with many other design features and dimensions.
* Model K and KK 1952–1953: 750 cc side-valve engines, using the 45 model bore and stroke
* Model KR (racing only) 1953–1969: 750 cc side-valve engines
* Model KH and KHK 1954–1956: 885 cc side-valve engines, using the 45 model bore, but with the stroke increased to 4.5625" (115.89 mm). This is the only small twin with a longer stroke than 3.8125", which is otherwise universal to the entire 45/K/Sportster line from 1929 to the present (exception: XR750, XB9 Buell).
X series Sportsters
* XL, Ironhead, 1957–1985: 900 cc (883 cc actual) and 1,000 cc Ironhead overhead-valve engines with cast iron heads
* XR750 (racing only) 1970–1971: 750 cc overhead-valve engines, iron heads
* XR750 (racing only) 1972–1985: 750 cc overhead-valve engines, alloy heads
* XLCR Sportster (cafe racer)1977–1978: 1,000 cc overhead-valve engines, iron heads
* XR1000 (racing only) 1983–1984: 1,000 cc street model using XR racing cylinder head and other XR engine parts.
* XLR (racing only): 883 cc overhead-valve engines, iron heads
* XL, Evolution (also known as the "Evo"), since 1986: 883 cc, 1,100 cc and 1,200 cc Evolution overhead-valve engine, alloy heads
Source : en.wikipedia.org/wiki/Harley-Davidson_Sportster
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