When the Harley-Davidson Sportster was initially introduced into the product line for the 1957 model year, William J. Harley was the head of the Engineering Department at the Motor Company. He was the son of William S. Harley, one of the founders of Harley-Davidson. William J. Harley graduated from the University of Wisconsin in 1934 and immediately began working at Juneau Avenue in what was known then as the Experimental Department. He swiftly moved to the Design Department and in 1942 became Assistant Chief Engineer and then in 1943 was promoted to Chief Engineer. In 1957, William Harley was named to the post of Vice-President of Engineering and it was, then, under his immediate guidance that the 1957 Sportster was introduced.

The direct ancestor of the Sportster was the K Model, introduced in 1952. The K Model was a side valve. Eventually, because of the success with the 61, it was known that the K model would evolve into an overhead configuration. Introduced as a 45 cubic inch, it was bored to 55 cubic inches and became the KH.

The overhead valve engine was a logical next step because of the delivery of higher horsepower and the Sportster was introduced with the transmission integral within the crankcase and was one of the first motorcycles designed with pre- unit construction.

The first Sportster was a 55 cubic inch V-Twin four stroke, with four speeds. It came with an oil bath primary chain drive and a completely sealed dry clutch. This offered extreme durability and long life to the chain and sprockets, and permitted the high efficiency of a dry clutch eliminating, for example, the sluggish wet clutch start-up process (referred to by many as 'morning sickness'). Harley-Davidson's Engineering Department experimented with a number of different overhead valve configurations before finally deciding upon the 45-degree V-Twin that, of course, had been traditional on Harley-Davidson motorcycles. The 45 degree V-Twin Sportster engine design was executed not merely to stay in line with tradition, but also because, as with a 90-degree V-Twin, with cylinders extending to the sides with a fore and aft crankshaft, which was one of the possibilities, with utilization of the chain drive, it was absolutely necessary from an engineering perspective, to have the sprockets lying in a plane that would be parallel to the direction of the machine itself. A transverse crankshaft would mean the machine would lean in one direction when accelerating because of torque reaction. So heritage and innovative engineering combined in the resultant 1957 introductory model. This interactive process of tradition merged with technology is the Harley-Davidson design process to this day.

The compression ratio was very deliberately set at 7.5 to 1 because in 1957 the engineers wanted to ensure that they did not over-rate it. When they found that the Sportster engine would withstand the heat and such involved with running at this high compression ratio reliably, they raised the ratio to 9 to 1 and therefore increased the power considerably. The bore was three inches and stroke was three and 13/16 inches.

1957 Sportster

In 1958 the Sportster evolved. The cam shaft small gears became an integral portion of the shaft and were not keyed. The sprocket shaft carrying the drive gear was increased by 1/8th of an inch in diameter. These alterations were instituted to increase the durability and strength of the lower end for a longer life span.

In 1959 the Sportster CH was brought into the model lineup. The CH was a stripped version of the motorcycle, with a magneto/generator ignition and then the H was the road-type with a battery charged ignition. CH is usually referred to as designating "Competition Hot." Both the CH and H versions had the very same engine and performance curves but the H model, in 1959, had more accessories and was setup for much more rider comfort and touring. All Sportsters in '59 got a horsepower boost by virtue of a high lift front intake cam and a newly designed contour on the exhaust cams. The shaft between the main feed pump and the return gears in the oil pump was sealed with neoprene, which was handled to prevent leakage of oil into the engine crankcases.

In 1960 new shock absorbers were introduced. Actually, these were of the same type that had been previously introduced on the Duo-Glide. These suspension system provided a more variable riding experience, such that in the mid-range engine output the ride was softer and highway cruising therefore more rider-friendly.

In 1961 the Sportster was restyled with what was termed a "Jet Age" concept. The gas tank was also redesigned to permit a more convenient location for welding.

In 1962 the only change was the manufacturing of the upper fork bracket out of aluminum which resulted in a reduction in weight and material cost.

For 1963 the third gear transmission ratio was dropped from 1.381:1 to 1.323:1 which made for an overall drive ratio in third of 5.56 for the H and 5.85:1 for the CH. This meant that there was a closer ratio between third and fourth gear. The rider could grab more jump out of third gear at the top end.

1964 brought full width aluminum wheel hubs, which radically improved braking and die casting them made for manufacturing economy and better cooling. The same year brought aluminum tappet guides plus a leak-proof poly-acrylic clutch oil seal.

In 1965, anticipating electric starting, the Sportster switched from six volt to twelve volt. The pistons were alloy coated for protection. This casting is rather like a metallic lubricant and lasts for the break-in period only. Ball-end control levers were supplied as a safety feature. Shock absorbers were once again improved with a new system on the rear for a smoother rate of internal control.

In 1966 the Tillotson carburetor replaced the Linkert. This new carburetor was a diaphram carb with a larger venturi. This meant greater fuel flow to the engine and consequently increased horespower. The Tillotson also was insensitive to lean and tilt while the bike banked corners and climbed hills, so performance was radically improved overall. The Racing Department developed "P" cams for the Sportster this year, which have a different curve and give a higher horsepower from approximately 3500 to 5500 rpms. The huge jump came at 4000 which was cruising speed. "P" cams worked as efficiently as the high lift cams on the top end. The distributor timer was revised to make it easier to adjust.

In 1967 the electric starter was introduced on the XLH. (It was not until 1968 that the kickstarter was deleted.) Also, the shock absorbers were improved once again, this time for easier control relative to handling and individual rider adjustment capability.

The shape of the 1200 power plant for the future.

A program began in mid-year of 1963 to design a system of electric starting for the FL, keeping in mind, that the same or similar system would ultimately be applied to the XL. The Project Engineer for the Electric Start Program was Les Ford, who later became the Sportster Project Engineer.

The result of the FL electric starter project was the Electra Glide in 1965 (though the year before there was an electric starter offered on the 45). Numerous starter problems were resolved, one by one, the main problem was in the bearing situation to ease the load on the starter motor. Once that problem was successfully handled, going to needle or roller-type bearings to reduce friction, the whole system fell into place and was applied to the Sportster. Cranking over 55 inches was a lot less stressful than cranking over 74. They changed the gear ratio somewhat and designed it with quicker cranking speed.

An interesting and educational note relative to the Sportster electric start evolution, is that after the FL electric starter production was well underway, it was discovered that current loss through the wiring harness was considerably greater in production than in the experimental stage, where the terminals were all hand-crimped. So on the XL, lessons learned, Harley-Davidson engineers revised the circuit to reduce the number of contact points and shorten the length of wiring. Better circuitry design was used so the leads were connected for better electrical efficiency flow on the XL. Well over 90% of all that the engineers needed to know for the XLH starting system had been learned from the FL program.

The Harley-Davidson Sportster, from its introduction in 1957, through the introduction of an electric starter in 1967, immediately became America's first sport/muscle bike, beating the foreign competition in the sport category. In fact, it runs alone as the primary muscle bike and does so with classic variability. A rider can strip it for a racey look or accessorize it for a mini-Twin appearance. And, of course, one can buy a Sportster right off the Dealership floor looking either way. No matter how it appears, sparse or dressed, it runs like a muscle bike should, with power and presence. With the styling, engineering and heritage that only the Harley-Davidson Motor Company can bring to the sport, it's very lifestyle was solidified. From 1957 through 1967 the Sportster went through ten critical years of improvement, and in 2003 is still one of our most intriguing models.

Bikernet Reader Corrections:

I'm amazed. Did you think that this guy doesn't make mistakes?

"The Triumph Speed Twin was introduced in 1949"
1937

"the W-series, introduced in 1941"
1937

"sportier version of the KH was introduced in 1956, replete with hot cams, polished ports and was called the KHK"
1954

"knawed" Doesn't he even speak English? It's
GNAWED.

"The XL-series hit the dealers in 1957"
1956

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