Factory Hot Rod: Hermann Koepf’s Brakeless K-Model Flat Tracker…
In 1952, Harley-Davidson introduced the Model K series in a bid to challenge the British parallel-twins that had become so popular on both the street and track. The K was the first Harley model to feature unit-construction — engine and transmission in the same case — and much of the design would be incorporated into the Sportster introduced in 1957.
The side-valve V-twins ranged from 750cc to 888cc in stock trim, and a dizzying array of model variations for various riding styles and racing disciplines was available, including the KH, KHK, KR, KRTT, KK, and several more.
The 1953 Harley KK 750 flat tracker you see here comes from our new friend Hermann Koepf (@hermannhead) of Munich, who publishes the motorcycle photography magazine BRUMMM, organizes Germany’s well-known and beloved flat track series KROWDRACE, and revived the Auerberg Klassik — the annual hillclimb in the Bavarian village where he grew up, which ignited his passion for two wheels as a boy. To say the Hermann is a fixture of the European vintage motorcycle community is an understatement.
Hermann does his wrenching in a rented underground garage in Munich. For the last several years, he’s been racing flat track on his 1967 Swanson-framed 250 Ducati, but the lightweight short tracker kept falling behind the big bikes on the larger tracks. It was time for an upgrade that would still qualify for the “True Gold” vintage class. Then a 1953 KK entered his orbit…
“In 2021, during the height of the COVID-19 pandemic, when we were celebrating a rather boisterous crowd-racing season-ending party at our friends’ place, the Berlin DIY workshop Craftwerk Berlin, one of my vintage motorcycle buddies mentioned that he was selling a 1953 KK.” -Hermann, BRUMMM
While the XR750 might get the lion’s share of the retrospective limelight, the earlier Harley K models were a dominant force in 1950s flat track racing, particularly the KR 750’s.
“Famous names like Carroll Resweber, Joe Leonard, Ronnie Rall, Bart Markel, Everett Brashear, and George Roeder dominated the competition on the 750cc KRs (the successors to the WL/WLA) in ‘Class C,’ a class designed to make the struggling dirt track accessible to the average rider on a production motorcycle (and to boost OEM sales).” -Hermann, BRUMMM
As a Ducati nerd, Hermann had to do some research to learn more about the KK. As it turned out, the KK was a one-year-only factory hot rod, and just 1723 units were built.
“The KK (only produced in 1953) was a hotter version than the standard Model K, had much larger racing cams, carb modifications, head modifications and cylinder porting to match. It used the old WR racer’s valves and guides and the new KR racer’s lightened roller tappets. Compared to a real KR the stroke is still a little longer from a standard Model K.” -Hermann
What’s more, when Hermann tracked down a previous owner of the bike from Philadelphia, he learned the engine had been rebuilt by well-known K-model tuner “Chico” with tons of go-fast goodies:
“KR roller tappet valve train with 2″ intake valves (instead of 1 3/4″), ‘ported KK heads,’ and on top of that, KR cylinder heads with enlarged combustion chambers and steeper camshafts with longer travel — similar to a 54 cubic inch KHK, which was later built as a sport version with just under 900cc [883cc]. Bingo!”
Hermann decided to transform the bike — which had previously been drag-raced — into a flat tracker that resembled the old KR 750 machines. However, he had quite a long road ahead of him to get the KK into racing trim.
He disassembled the bike down to the bare frame and took the engine and a new set of oversize pistons to a friend and speedway engine guru in the Allgäu region.
“I had to repair/weld the usual cracks in the cylinder heads (which came also from a KR racing model) around the bronze inlets for spark plugs; also I replaced the worn out pistons and put a new Mikuni 38mm carburetor on it with handmade aluminum cover around the K&N air filter. I also replaced the heavy side cover of primary drive into a light weight sheet metal cover, for which I had to remove the long damper on front sprocket to make it fit.”
While we could simply provide a list of parts that went into the build, it adds a very meaningful layer to the story when you realize how nearly every component on this flat tracker has a friend or story behind it. Says Hermann:
“I promptly found a John Penner subframe on the classifieds, which, as luck would have it, was being sold by a friend here in Munich — a lucky shot, so to speak! A Berlin-based sports enthusiast sold me a 19” wheelset with old Jawa speedway hubs, and I snagged the short 35mm Ceriani replica fork from my friend Alessandro A. in Treviso.
Technical drawings for new steering head bearing cups and an aluminum quick-release sprocket adapter were quickly drawn up and sent to my longtime Allgäu metallurgist friend, Hans S., with a request for contract manufacturing.
Bates footpegs flown in from the States were fitted to the frame, and a matching handlebar with a Tommaselli throttle grip was mounted to the Marzocchi triple clamp.
A friend from Hamburg kindly provided me with his original Trackmaster tank, so I had five fiberglass replicas made in Italy (sorry, they’re all sold out!). Even if this tank and the Hoosier flat track tires (and a few other parts) aren’t exactly period-correct, the sum of these individual parts results in what I consider a very harmonious design with a thoroughly contemporary overall impression, refined with a few white color accents on the tank, seat, upholstery and exhaust pipes – à la Joe Messaros’ KRs in the late 1960s.”
As you can see, this bike is built as much on passion and community as steel and aluminum. The list goes on: Master metalworker Martin K. from Lower Saxony fabricated the handmade aluminum cover for the K&N air filter, while the Mikuni VM-38 carburetor itself comes from Topham in North Rhine-Westphalia.
The cylinders were welded and repaired with new spark plug bushings by a welding guru in Sweden, which took more than a year. When Hermann finally had everything buttoned back together, he took the bike above ground for its first start…no dice. He suspected an ignition timing issue.
“After consulting my long-term letter friend Steve M. from Montana as well as the Norwegian flathead prophet (and, incidentally, a rather fast Krowdrace participant) Gunnar S., the suspicion grew that Chico the K-Amigo had installed not a standard KK crankshaft, but something with a flywheel and, let’s say, an ‘alternative’ degree marking – therefore, the magneto positioning couldn’t be correct. Back onto the lift, heads off, and highly professional setup of measuring devices to check the piston travel. The 7.87 millimeters of piston travel before top dead center were far too little for the camshafts used, which is why, on Norwegian advice, I adjusted the magnet to approximately 10 millimeters of piston travel (which should correspond to about 36 degrees of ignition advance) and screwed everything back together for another start attempt.”
Again Hermann brought the 72-year-old battler to the surface for go — this time, the cranky old twin fired right up!
“What a sound! And what a mechanical shudder from the whole machine! I let the engine warm up for a while before taking it for its first cautious spin around the backyard… Back on the kickstand, I let the engine run for a while longer — much to the delight of a passing motorcycle enthusiast who came down from the 17th floor of the neighboring office building to find out what that deafening noise was all about, ha!”
Hermann now races this very rare, very special KK 750 tracker in the KROWDRACE series and other European flat track events. He runs it brakeless, of course, as the Class C 750cc machines were raced back in the day, and regularly lines up against other Harley WLs, WLAs, XRs, Sportsters, and even a pair of KRs out of Berlin.
Building and racing a machine like this wouldn’t be possible without a hearty dose of grit and passion, as well as a community of friends and fellow racers to count on for parts, advice, and support. In our eyes, this KK 750 flat tracker is much more than a machine — it’s a testament to passion, friendship, and community.
Thank you, Hermann, for bringing this old side-valve hot rod back to life and sharing the story with the rest of us. We look forward to seeing more of it at KROWDRACE and other events!
About The Builder / Racer
Hermann grew up in a Bavarian village near the famous castle Neuschwanstein, where the annual hillclimbing competition sparked his passion for everything on two wheels. He took his first ride at the age of five on a 1930s hand-shifted Sachs Presto before he began wrenching in his garage, riding, and racing mostly carbureted Ducatis.
Now living in Munich for 35 years with his family, he runs a marketing and design office. He writes and shoots for international motorcycle and lifestyle magazines as well as for corporate commissions, and is one of the two publishers of BRUMMM moto photography magazine.
With KROWDRACE he sets up German flat track racing events, where he races on this Harley KK as well as the 60s Swanson-framed Ducati short tracker he built few years ago. And finally, he is now the reviver and head of the organizing committee of the hillclimbing revival event in his home village called Auerberg Klassik!
More Photos
Follow the Builder
Instagram: @hermannhead
KROWDRACE: www.krowdrace.de | @krowdrace
BRUMMM: www.brummm.com | @brummm_chronicles
Photography: Luis Ganssloser, Jan van Endert, Kati Dalek, Hermann Köpf
Great story and history of a clean machine! Interesting how the pillion seat is utilized with the seat to work as one appose to choosing a different seat configuration all together. I dig this build, it’s just a straight forward race machine with a cleanliness about it. I am a huge flat track fan and I wish I could have raced prior to becoming disabled. I just dig everything about this bike, and the simple color choice just set it off perfectly!
I wish the owner much success in his future racing and hats off to him and those involved in getting this machine to the dirt.