Hell-Raiser: 1956 Harley-Davidson KHK

The British invasion

The KHK story starts shortly after World War II. Before the war, England had an extensive motorcycle industry, with most British motorcycle companies making large numbers of inexpensive motorcycles for the get-to-work crowd, along with a few high-end sporty bikes for riders who could afford them.

Civilian motorcycle production was suspended for the duration of World War II. After the war, British manufacturers had to guarantee that 75 percent of their production would be sent overseas. England was crushed by war debt and had to export most of its manufactured goods to pay it off. As a result, most of the larger British motorcycle manufacturers set up dealer networks in the U.S. and started producing larger numbers of their top-of-the-line bikes for export. This push received a boost after Indian’s failed attempt to remake itself as a manufacturer of lightweight motorcycles in the British mode with a new line of vertical singles and twins that, unfortunately, suffered from major design flaws and serious quality control issues. Making matters worse, in the midst of all of this England devalued the pound, making British motorcycles cheaper than American-made Indians. Ironically, Indian ended up becoming a major importer of British motorcycles and many Indian dealers started selling British motorcycles.

At first, Harley-Davidson ignored the flood of Triumphs, BSAs and Nortons pouring onto U.S. roads. In the late 1940s, Harley was manufacturing 61- and 74-cubic-inch overhead valve V-twins, 45-inch sidevalve V-twins and 125cc 2-strokes – which, incidentally, were very popular. The big overhead valve twins were heavy touring machines with long wheelbases. The flathead 45s were slow utility bikes. Both had tank shifters and foot clutches. The new imports were light, with high revving overhead valve engines, foot shifters and hand clutches. They were easier to ride and handled well.

Eventually, Harley became alarmed at the number of British machines on the road. Its concern probably had a lot to do with slowing sales. World War II veterans were getting married, moving to a house with a white picket fence and trading in the bike for a washing machine. While 29,612 Harleys were sold in 1948, that number dropped to 23,861 in 1949 and plummeted further in 1950, with only 17,168 Harleys sold. Harley’s future didn’t look bright.

Resist or compete

Harley-Davidson first tried asking the U.S. Government to raise tariffs on British two-wheelers. In September, 1951, hearings were held before the United States Tariff Commission, and they didn’t go well for Harley. Believing that the Commission was going to deny the request (which they did in June 1952), Harley-Davidson went to Plan B – if you can’t fight them, join them. Still awaiting the commission’s final decision, Harley announced a midsize, sporting machine to compete with the British bikes.

Introduced for the 1952 model year, Harley’s new midsized sport bike was named the K model. It was mostly a very up-to-date machine, with a left hand clutch and right foot shift, like the imports. It had telescopic forks and swingarm suspension at a time when some British motorcycles, notably Triumph, still had rigid rear ends. The engine was built in unit with the transmission and clutch, and the cylinder heads were aluminum. But it was, oddly, still a sidevalve flathead, just like the W model 45-cubic-inch machines that had preceded it, but with a 6.5:1 compression ratio versus the older bikes’ standard 4.75:1.

There were probably many reasons why Harley gave the K model a sidevalve top end. Although no records are available from Harley to answer this question, it’s likely that Harley’s slowing sales resulted in belt tightening in the engineering department. Further, management probably still had vivid memories of the disastrous 1929 introduction of its flathead V model twins, and did not want to chance a repeat.

When the K model appeared in late 1951, it made 30 horsepower, weighed 400 pounds, and was good for about 80mph. The overhead valve 650cc Triumph Thunderbird made 34 horses, weighed 385 pounds and was good for over 90mph. A few road-going KR’s, dubbed KK, were manufactured, and they could run right up there with the best of the imports, but there were so few of these that they were not even listed on the Harley order blank.

The K model was likely intended as a stopgap measure while a sporty overhead valve middleweight was developed, which finally came with the 1957 Sportster. Possibly (I have not seen any official documentation on this question) the overhead valve cylinder head was taking longer to develop than anticipated, but whatever the case, something had to be done to up the power of the existing K models. They were good bikes – just slow, and slow bikes didn’t sell.

The racing version of the K model, the KR, was however very fast and a successful contender in American racing for years. It had ball bearing main bearings instead of the roller bearings used on the K model, better breathing and other modifications, and weighed a lot less. Even so, it is a lot easier to get speed and power out of an overhead valve engine, which all the Brit bikes had.

Bigger is better

“There’s no substitute for cubic inches” was the speed mantra in the 1950s. Stroking engines – changing their displacement by changing their stroke – was popular among hot rodders and drag racers, so in 1954 Harley stroked the K, increasing capacity from 45 to 54 cubic inches (or 883cc, a displacement shared by base Sportsters ever since), while also putting in bigger intake valves and improving the porting. This bumped output from 30 to a claimed 38 horsepower. All of this was standard issue speed work for the time, and it did make the bike (now named the KH) faster. Cycle magazine took a KH to the drag strip and clocked it through the quarter-mile at 14.75 seconds. Top speed was 95mph. Unfortunately, dry weight was now 440 pounds.

The KH was not a best-seller. Harley dealers managed to sell 1,579 of them in 1954. The little Hummer 125 single actually sold better. The next year, Harley engineers came up with the fastest road version of the K model yet: the KHK. The KHK had the same displacement as the KH, but was treated to more aggressive cams that were close to the 1953 KR factory racing cams, more extensive porting work with polished ports, and KR valve springs. Output was a claimed 52 horsepower, and rumor had it that Harley’s race department was involved in building KHKs, or at least provided some of the special parts, rumors that may have been sparked by period ads. “A special model like the KHK is not produced in the normal channels of production. To get that extra horsepower takes time and loving care. The quantities, that can be produced, are rather limited and sufficient time must be allowed to fill orders,” stated one ad, urging potential buyers to get their orders in early.

The KH and KHK lasted only until 1957, when the sporty overhead that Harley had needed to sell since the late Forties finally saw the light of day. Strangely, the 1957 XL and XLH Sportsters (H = higher compression) looked like junior Panheads. As a result of pressure from West Coast dealers, in 1958 Harley started building the XLCH, a version of the Sportster that looked like a flat tracker. Sales took off and never looked back.

All K models are rare, but KHKs are the rarest of the rare: 449 were built in 1955 and 714 in 1956. Not letting that fact get in the way of a good thing, shady shade tree mechanics have for years been converting plain Jane K models and KHs to KHK specs and altering the factory stamp on the engine to match. Buyer beware.

Craig Horner’s KHK

The bike shown here is an authenticated 1956 KHK. “It was built the year I was born,” says owner Craig Horner, who has been a motorcycle enthusiast since childhood. “Working on bikes came naturally to me. My parents had a Benelli, and I helped my father work on his dune buggies.” Craig got bit by the old bike bug 25 years ago, when he started going to the Mid-America auctions. “I’m not interested in later stuff at all. I go for bikes from the Teens up to the Forties and some Fifties stuff. I like to work on early American bikes, and I’ve bought and sold several early Teens Indians. It’s a hobby.”

Craig purchased the KHK on eBay in 2008. Believe it or not, the paint and most of the components are unrestored. “I realized from the photos that it was really close to the original. One item that I wasn’t sure about was the yellow stripe. It was painted on top of the black main color, which I thought was a little odd, but I researched it and found that was the way the factory painted the tanks,” Craig says. “It was running when I bought it, but the wheel spokes were chrome plated, which was incorrect, and someone had shrink wrapped the wiring. To restore the bike to the original condition, I had to very carefully remove the shrink wrap.” The wiring harness was original and in good shape except for the shrink wrap. Sportster expert Dave Carleton helped Craig find authentic-looking cables. The bike has been judged under Antique Motorcycle Club of America rules and been found to be mostly correct, with a few minor issues that Craig corrected before the photos for this article were taken.

Perhaps surprisingly given its rarity, Craig does occasionally ride the KHK. “Shifting on the right side was a challenge for me,” says Craig, who like many riders is more used to “standard” left-shift machines. “I worked at it until I got comfortable on the road. It helped that several of my friends ride bikes with right side shift. Really, I prefer shifting on the left.

“The KHK is tough to kick over, but once I get it going and warmed up, it pulls from zero rpm. You do have to let the bike warm up, but once it is warm, it rolls out. The brakes are good. Brakes are one of the first things I check when I get a bike, and they were sound. I put new cables on everything, however, just to make sure. I am adamant about the safety of my bikes.”

Craig says the KHK takes premium gas and he uses multi-grade 15/40 or 15/50 oil. Some restoration experts think Fifties bikes will leak if you use multi-grade oil, but Craig says he has had no problem. If the bike will be sitting for a few months, Craig will drain the oil from the sump, but notes that “if you run it all the time, you don’t have to drain it.” There is an oil filter in the oil tank, and Craig has added an in-line fuel filter, which he removes when he is showing the KHK. “So far I have not had any trouble with the Linkert carburetor, but from previous experience, no fuel filter means a clogged Linkert.”

The KHK was the closest road machine to Harley’s racer, the KR that ruled the tracks in the 1950s. “I like the look of Harley flatheads,” Craig says, obviously fond of his Fifties hell-raiser. “This one is special. It’s the last year – and it has that high compression engine.” A non-conformist if ever there was one. MC