As one of the most prestigious names in the motorcycle industry, Harley-Davidson needs little introduction. The American brand started producing motorcycles in Milwaukee, Wisconsin in 1903. This started a reign of over a century in pole position as the most successful motorbike manufacturer in the United States.

Throughout Harley-Davidson's long history, several iconic bikes have each gained a die-hard cult following and worldwide fame. One of these is the K-Series that ran from 1952 to 1956, especially the famous KH model. It was a KH bike that was Elvis Presley's first Harley, and the brand became associated with The King for the rest of his life.

The K-Series also had a prestigious racing pedigree, achieving a lot of success on the American racing circuit. The model was designed to be a sportier, mid-range alternative to the mile-eating Panheads that were gaining popularity among motorcyclists. Despite its short production life, the K-Series is one of Harley's most famous bikes and continues to be popular with restorers and bike builders today.

In this article, we'll delve into the history and cultural impact of the Harley-Davidson KH and K-Series to find out why the range is so legendary and why it still has a dedicated following today.

Development & History

When a wave of nimble, powerful British motorcycles began gathering popularity in the States during the early 1950s, Harley-Davidson had to fight back. While the larger Panhead models were the kings of cruising down the newly-emerging highways of post-War America, they weren't direct competitors with British motorcycles.

Enter the K-Series, starting with the original Harley-Davidson K in 1952. The new bike was designed to be a mid-weight motorcycle that could battle the British invaders with pulsing power and nimbler handling than the Panhead. The original K produced 750cc – equivalent to 30 horsepower – and was the most innovative model that Harley-Davidson had produced at the time.

In a first for the American marque, the K had hydraulic suspension at both ends of the bike, with hydraulic front forks and a swing-arm and hydraulic shock absorbers at the back. Its impressive handling ability made it a natural racing bike, and the K-Series dominated national championships almost completely by 1956.

Throughout its four-year production run, the K-Series underwent several changes as Harley-Davidson continued to develop the lineup. The original K bike was available from 1952 to 1953 before being joined by a faster, racier version – the KK – for 1953. Both models were replaced by the KH in 1954. The association with Elvis began in 1956 after The King purchased a KH model in the iconic “Pepper Red” paint job.

This new edition featured a more powerful 888cc engine and was available until the K-Series was stopped in 1956. Alongside the KH, Harley also released another high-performance edition called the KHK. To celebrate Harley's first 50 years of producing motorcycles, a special edition KH bike – the Golden Anniversary KH – was released in 1954 with limited-edition icons on the front fenders.

But despite yearly updates, the model soon had to make way for the next generation. In 1957, the K-Series morphed into the best-selling motorcycle in history – the legendary Harley-Davidson Sportster. By paving the way for this iconic model and gaining its own cult following, the K-Series cemented its hallowed place in motorcycle history.

Engine

To compete with British marques like Norton and Vincent, Harley-Davidson needed a mid-weight bike of their own. What they came up with was the K-Series, with the first model being released in 1952. The first incarnation had a 30 horsepower, 750cc V-twin engine with finned aluminum cylinder heads for improved cooling.

This new engine was a complete redesign for Harley, but it achieved 100 mph in a speed record run in 1952. Harley could finally fight back against the British bikes. The K had a four-speed transmission system that involved a hand-operated clutch and foot-operated gear shifter. Both the engine and the transmission were corralled in the same casing to save weight.

The K's transmission setup, with the clutch on the left-hand side and the gears on the right, was ideal for motor racing, and over its production life the K-Series became the dominant racing bike in America. But as Harley's British competitors kept improving their bikes, the K-Series had to evolve as well.

In 1953, Harley released the KK, which was a slightly souped-up version of the K. Inspired by racing bikes, the KK had larger cams and several alterations to the cylinder heads and the carburetor. The cylinders were also ported. Both the K and KK models were replaced in 1954 with the KH, which now featured a 54.2 cubic inch engine rather than a 45.1 cubic inch power plant. The KH bikes had a longer engine stroke and could produce 888cc.

Much of the engine was redesigned, with bigger intakes, taller cylinders, updated flywheels, and new ports. This also resulted in a larger clutch and a bigger power output of 38 horsepower. On the drag strip, the new KH outclassed the original K by over two seconds on the ¼ mile. Harley-Davidson improved this even more with another high-performance edition – the KHK. Both the KH and the KHK would continue to be produced and improved until 1956.

The 1954 bikes also incorporated a “trapdoor” engine case for better access to important components, and the final editions in 1956 had polished components and an updated air filter for smoother performance.

Chassis

But simply having a good engine wasn't enough to battle other manufacturers. Harley-Davidson also had to design the K-Series with good handling in mind. The original K bike was Harley's first commercial production model with hydraulic suspension at both the front and back of the motorcycle. This gave the K a good ride as well as more nimble handling than the larger and heavier Panhead.

The K's hydraulically-dampened telescopic front forks were accompanied by a rear swing-arm and hydraulic rear shocks. This improved suspension style was comfortable for riders who wanted longer road trips across the rapidly-growing highway network that began to snake across America. But it also helped the K-Series to become one of the most dominant racing bikes in the 1950s.

For civilian models, the chassis and suspension weren't really changed until the release of the KH model in 1954. To improve the handling, Harley altered the rake and tail of the bike and made the steering column thicker to provide more stability. The rear shocks were also given new chrome coatings, replacing the old plastic ones.

The biggest chassis change to the K-Series came in 1955 with a complete revamp of the existing frame. The steel tubing on the frame was replaced by chrome, and the entire chassis was altered to create a lower riding position for the seat. The front forks became an inch shorter to generate better handling for the KH & KHK bikes. This created a much sharper-looking bike with sharper handling to match.

Because the KH & KHK models now boasted extra power, Harley also had to increase the size of the rear spokes and wheel hub to stop the tires from being torn to pieces. But in 1956 – the final production year for the K-series – the chassis was redesigned yet again.

The engine was dropped slightly within the frame to improve the bike's center of gravity. The steering neck was thickened again, the rear shock absorbers were shortened, and the seat was lowered even more. A stronger frame around the seat kept comfort within norms for the K-Series and a sturdier swing-arm was added.

Impact On Motorcycle Culture

While it might not have had the movie pedigree of later Panhead Harleys, the K-Series still boasted plenty of star power and had its own cultural impact.

Elvis Presley bought his first Harley-Davidson in 1956 from a dealership in Memphis. The King of Rock and Roll chose a “Pepper Red” 1956 KH bike and was accompanied by the bike during a photoshoot with Harley's official magazine - “The Enthusiast”. The shoot cemented a bond between star and marque that would last until Elvis's passing in 1977.

While he was still alive, Elvis sold his 1956 KH and continued his association with Harley-Davidson. It was bought by a man by the name of Fleming Horne, who eventually sold the bike back to Harley-Davidson in the mid-90s. The company has displayed the bike ever since in the Pop Culture exhibit of its dedicated museum.

The K-Series also boasted pedigree on the track. During one of the Golden Ages of American motorcycle racing, the K bikes were the undisputed masters. Their reliable power output and good handling made them a great foundation for racing bikes.

From 1954 to 1957, two of America's greatest ever riders – Joe Leonard and Brad Andres – controlled America's National Championships. Harley-Davidson actively encouraged the competition between the two riders, offering $1000 for each extra horsepower that they could coax from their K-Series bikes. Leonard won the championship three times in 1954, 1956, and 1957, while Andres pipped his rival in 1955.

From taking the fight to rival British marques to being associated with Elvis Presley, the four production years of the Harley-Davidson K-Series, especially the KH model, left a legendary legacy. What makes this heritage even more potent is that the KH formed the building blocks for Harley's most successful motorcycle of all time – the Sportster.