Thickly veiled in mystique, the Harley-Davidson Knucklehead engine is arguably one of the most iconic powerplants ever built. Nearly nine decades after its debut, the silhouette of those fist-shaped rockers still carries a kind of mechanical authority—part engineering milestone, part cultural shorthand. It’s the motor that dragged Harley into the modern age, and also set the groundwork for everything from postwar bobbers to outlaw choppers. Among American V-twin engines, there are none more captivating or desirable.
Justin Powers knows all of that. He also knows that reverence alone doesn’t keep a motorcycle running.
For the last fifteen years, Powers has been building board track racers and customs under the Bull Motor Company banner, fielding the same request again and again: a Knucklehead-inspired bike that looks right, feels right and doesn’t punish its owner for wanting to actually ride the thing. Not a museum piece, but a properly sorted, visually honest machine that captures the spirit of the early Big Twins without inheriting all their bad habits.
Eventually, the request became too consistent to ignore. So rather than building the same bike one customer at a time, Bull Motor Company made a different decision—one that’s rare in the custom world. They committed to a small production run, built around the most requested components, with an emphasis on reliability, serviceability and long-term ownership. A custom motorcycle with a warranty. Imagine that.
A foolproof foundation was selected for the project—an OE-type Harley FL wishbone frame—standard fare for Big Twins from 1948 through 1954. It looks right because it is right, continuing Harley’s uninterrupted sloping line from the neck to the axle plates. Aside from a few omissions, like the toolbox mount, it’s left largely stock for a period-correct look.
The wishbone frame has been fitted with every style of front end over the years, but for this project, only an OE-type springer would do, and this one ticks all the right boxes. Bull Motor Company fit the fork with inverted speedster-type bars, a scalloped headlight bucket and a disc brake from Performance Machine—because a little practicality here goes a long way on the pavement. Staying grounded in period, the wheels are spoked 16s wrapped in Avon Safety Mileage rubber.
Power comes from an S&S KN93, a modern interpretation of the Knucklehead that delivers the visual cues everyone wants with some practical tweaks. Displacement is up nearly 20 ci at 93 ci, producing 60-plus hp through half the rev range. S&S also completely updated the bottom end for improved longevity, and the oiling system is reworked to keep the engine from incessantly marking its territory.
The powerplant also makes use of S&S’s Super Stock electronic ignition system and Super E carburetor with a finned bird deflector. As for the final drive, there’s no more appropriate choice than the venerable Baker four-speed—delivered via an open chain.
Adhering to bobber basics, the bodywork is bare-bones and entirely purpose-driven. A distressed saddle provides seating for one, and a traditional bobbed fender is used out back. The scalloped fuel tank adds contemporary flavor to the build, but it’s hard to argue with the brass accents and the way the tank’s underside accentuates the Knucklehead’s rocker boxes.
The oil bag is another interesting piece. While its finned look jives with countless elements on this build, it’s actually based on the Harley Rocker FXCW. It took some fiddling to make it work, including chopping 4 inches out of the center and recasting it to fit the narrower FL frame, but the finished product looks tailor-made for this project in its as-cast finish.
Finishes were one of Powers’ big considerations with this project. He knew he wanted to build a bike with patina, but he was after something that looked well-aged, rather than crusty and forgotten. His biggest inspiration came from Colt M1911 .45 Auto, and it’s easy to spot the influence.
Various bits, including the fuel tank, rear fender, fork and exhaust, were chemically treated to produce the same black oxide finish used in gun bluing. In addition to its rich metallic color, bluing also provides long-lasting corrosion protection. The distressed leather saddle also closely resembles the look of the wood grips on early-production 1911s.
Digging deeper into the details, you’ll notice that the cast and polished aluminum bits on the bike also appear aged, and various oxidizers were used to create this effect. The frame itself was treated to an aged bronze finish that varies as it goes, and the brass parts used throughout also look like they have some miles on them. In a world where patina paint jobs can be divisive, Powers certainly found an excellent approach for baking authentic character into a new build, and he adamantly states that there’s no paint present on the bike.
While the Bull Motor Company Knucklehead is certainly visually captivating, the true magic is in its ability to seamlessly blend reverence and practicality. In this bike, the average onlooker sees a relic from yesteryear—just as intended. But a trained eye sees the parts that make it work on the open road, such as the hydraulic discs, oil filter, modern electrics and reliable new driveline components. And let’s not forget about the peace of mind that comes with a warranty.
So while a production run of Knucklehead customs sounds like a dice roll, Bull Motor has certainly done its homework to put together a reliable and striking combination, and we can easily see the demand for something with this level of show ’n’ go. Interested parties, please form an orderly line here.
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