The 1953 K Model

Motoring on Memory Lane by Martin Jack Rosenblum

The K-Model was brand new 1952 and led directly to the first Sportster in 1957. After World War II, the Indian Motorcycle Company introduced a line of middle-weight twins (and singles) with overhead valve engines. The Triumph Speed Twin, later to evolve into the famous Bonneville in 1959, was introduced in 1949 and was a successful, fast, middleweight motor- cycle. With the less successful Indian and the awesome Triumph threatening Harley-Davidson's dominance on the streets and tracks, the Motor Company introduced the K-Model.

The K-series modernized Harley's sport bike category. The K-Model had unit construction, hand clutch and foot shift, but still ran a side-valve engine. The racing version was termed the KR, and had hot cams, valves with more efficient flow, ball rather than roller main bearings, and a magneto whereas the standard K carried a distributor. Bore and stroke were 2.75 by 3.8125 inches on the K, exactly the same as on the W-series, introduced in 1941, that the K-series replaced. It weighed 400 Ibs. and ran approximately 30 bhp. It came with a beautiful 4.5 gallon gas tank, and customers had a choice of a solo or dual seat.

Appearing in 1954, the KH had the K's bore, but the stroke was lengthened to 4.5625 inches. Displacement increased from 750cc (45 cu. in.). The transmission was improved as was the clutch. The sportier version of the KH was introduced in 1956, replete with hot cams, polished ports and was called the KHK. By this time, however, Harley-Davidson engineers knawed at the new Sportster on factory drawing boards. The KHK was not built as performance oriented as it might otherwise have been.

The XL-series hit the dealers in 1957. Labeled the Sportster, launching one of the most famous and well-termed motorcy- cles in history. The XL was a pure, American hot rod motorcycle. It was the first American muscle bike, and today remains the most popular machine in its class.

In 1957, the XL engine was a K converted to overhead valves. It had a larger bore of 3 inches (compared with 2.75 inches for the K), and returned to the original K stroke. The larger bore meant bigger valves and the shortened stroke meant higher rpm. Both created much more capacity for power.

With new cast iron barrels and heads, new cams and flywheels, the Sportster was powerfully equipped and in the dealer's showroom ready to be accessorized with immediately available options such as dual seat (it came with a solo), a wide assortment of chrome bolt-ons, luggage rack, windshield, and saddlebags. The Motor Company offered the bike as a junior Big Twin, even though it was designed to be sportier. This made a great deal of sense because, while the Sportster was hot rodded, it was not really the super-bike of the day. Its appeal could be fitted to that of the Big Twin's but down-sized. In 1958, the XLH which had an optional, higher compression engine was made available. Also in the 1958 catalog is the XLC, which was a slimmed- down and more scrambler-oriented Sportster, and the XLCH, which was a higher-compression version of it.

The Sportster was as impressive as it was hoped to be, winning at the drags and on the streets, and it was very much in demand. As a result of the numerous options and varied accessory groups, probably no two Sportsters left the factory alike. Basically, though, the XLH had a larger fuel tank, usually a dual seat, paired exhaust pipes combining into one muffler, ignition timer, and coil, while the XLCH generally carried the smaller gas tank, solo seat (either solid or sprung), magneto ignition, and sometimes high, scramble pipes or separate exhaust pipes and mufflers for each cylinder coming out on the right side.

The new 883 custom with sleek tanks and forward controls for 2004

In 1962, the magazine, Cycle World, road tested and reviewed an XLCH and reported a quarter-mile time from a standing-start of 14.3 seconds, and 0-60 mph was clocked at six seconds. The top speed was rated at 122 mph. The early Sportsters were quick and could easily compete with the British imports that ruled the corner stoplight drags.

The Harley-Davidson Sportster has always been a unique machine. It is an exciting motorcycle and has been ridden by those wanting a mini-Big Twin, those seeking to have an American sport bike. For 41 years the Sportster has been a premier hot rod Harley, and it has evolved not only in terms of factory revisions but also in the hands of riders who continually revise its function and performance.

A Bikernet Reader from the Victory Library wrote in with the following comments:

Corrections damnit:

"it was bored to 55 cubic inches and became the KH"
He evidently didn't read his own article - stroked, not bored.

"the Sportster ... was one of the first motorcycles designed with pre- unit construction"
He evidently didn't read his own article - unit construction.

"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"
I have no idea what this means, and neither does he.

"high lift front intake cam"
Used with the old rear intake cam?

"1964 brought full width aluminum wheel hubs"
Front wheel only.

"developed "P" cams for the Sportster this year (1966)"
"PB" cam, "P" cam is older (1962?)

There's probably more, but I'm too lazy to look it up - this is just what I remember off-hand.

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