The DAH Harley-Davidson Factory Racer
After dominating the racing scene since they first entered the Dodge City 300 back in 1914, Harley-Davidson found itself in a very different position by the late 1920s. Hillclimb racing had spread across the United States, and both Indian and Excelsior were fielding motorcycles that were beating the Motor Company weekend after weekend.
That mattered. Back then, winning races on the weekend was still closely tied to selling motorcycles during the week. If Harley-Davidson was going to stay visible in one of the most popular forms of motorcycle competition, it needed something more serious than another modified production machine. The answer was the DAH.
Harley’s Hillclimb Problem in the Late 1920s
The DAH came out of a period when hillclimb racing had become a specialized arms race. A hillclimber did not need lights, fenders, comfort, or road manners. It needed a motor that could pull hard, gearing that worked for a short and violent run, a chassis that could launch straight, and enough traction to claw its way up loose ground.
Indian and Excelsior had pushed hard in that direction, and Harley-Davidson’s older approach of adapting existing motorcycles was no longer enough. The DAH marked a change in thinking. Instead of starting with a catalog motorcycle and trying to turn it into a racer, Harley built a dedicated 45-inch class factory competition machine.
Harley-Davidson carried the same purpose-built approach into speedway racing with the 500cc CAC in 1934.
A Purpose-Built 45-Inch OHV Racing Motor
The DAH engine was based around a 45 cubic inch, roughly 750 cc, V-twin, but it was nothing like Harley-Davidson’s ordinary side-valve production motorcycles of the period. The big change was the overhead-valve top end. At a time when Harley’s street line had not yet moved to overhead valves, the DAH was already using that layout for factory racing.
The motor also had one of the most recognizable exhaust arrangements Harley ever put on a competition machine. Each cylinder used one exhaust valve feeding two exhaust outlets, giving the motorcycle four separate exhaust pipes. That four-pipe look is one of the easiest ways to spot a DAH in period photos and museum displays.
The DAH also gave Harley-Davidson its first recirculating oil system. Production Harley-Davidsons would not get that sort of oiling system until the 1936 Knucklehead, but the DAH program was already using it in a racing environment years earlier. For a hillclimb motor that had to run hard and survive repeated short bursts of abuse, that was a serious step forward.
Later DAH machines were associated with Schebler racing carburetors and alcohol fuel. As with most small-batch factory racers, there was not one clean showroom specification that applies perfectly to every DAH. The program changed as Harley learned what worked, what broke, and what could be improved before the next climb.
From Early DAH Frames to the Updated Factory Hillclimber
Experimentation with the DAH began in 1929 and continued through 1933. During that period, roughly 20 to 25 DAH machines or engines appear to have been produced, depending on how the surviving evidence is counted. They were not normal production motorcycles. They were factory and favored-rider racing machines, and they were assembled with different combinations of frames, handlebars, gas tanks, transmissions, and other competition parts.
The first DAH versions used a single-downtube frame. Later versions moved toward a stronger and lighter dual-downtube or duplex-style frame arrangement, matched to a trailing-link front suspension. Period descriptions and surviving-machine research do not always use the same terminology, but the direction is clear: Harley kept refining the DAH chassis as the factory chased a better hillclimb motorcycle.
At least four DAHs were reportedly recalled to Milwaukee in 1932 for major updates, including a new lightweight chassis. That fits the larger story of the DAH as a moving target rather than a fixed production model. The machine was developed in public, in competition, and under pressure from Indian and Excelsior.
John Grove, Joe Petrali, and the DAH Racing Record
The DAH made an impression almost immediately. In its debut race in 1929, John Grove rode a DAH to victory near Pittsburgh, Pennsylvania. Harley had the machine it needed, but that did not mean Indian and Excelsior suddenly disappeared. During the 1929 and 1930 seasons, Excelsior still took the national title, and Indian was on top in 1931.
Harley’s breakthrough came after Joe Petrali joined the factory hillclimb effort. Petrali was already one of the best-known motorcycle racers in the country, with victories in board track racing, dirt track competition, and other forms of racing during the 1920s. Harley brought him in as its only factory-sponsored hillclimb racer, and the decision paid off.
With Petrali at the handlebars, Harley-Davidson won the national hillclimb title in 1932. He repeated in 1933, then added more national hillclimb titles in 1935 and 1936. Those titles are the part of the DAH story that usually gets remembered, but he was not the only rider putting Harley’s factory hillclimb machinery in front of spectators.
Windy Lindstrom, Herb Reiber, John Grove, and other riders were also part of the DAH-era racing picture. Period race reports from the early and mid-1930s show Harley riders winning or setting fast times at places such as Indianapolis, Spokane, Portland, Bethlehem, Hershey, and Hornell. The DAH program gave Harley-Davidson a way back into serious hillclimb competition at exactly the time the factory needed it.
The 1935 season was especially strong. Petrali won both 45-inch national honors at Hornell, and period coverage credited Harley riders with complete domination of the 45-inch class. At Bethlehem and Hershey, Petrali again took 45-inch wins. By the middle of the decade, the DAH had done what Harley needed it to do: it put the factory back in front of hillclimb crowds.
The DAR Road Racer: DAH Mechanicals for Europe
The DAH engine also led to a rare road-racing derivative known as the DAR. Older summaries sometimes describe the European road-racing machine as a one-off, but the better reading is that Harley built a very small batch of DAH-based DAR road racers in 1929 for European competition. At least four are reported in later research, with Paul Weyres of Germany being the best-documented rider associated with the type.
The DAR was not simply a hillclimber with longer pipes. It used DAH mechanical ideas in a motorcycle changed for road racing rather than climbing steep dirt hills. The road-racing version used longer exhaust pipes, road-racing chassis changes, and a return-oil or dry-sump arrangement. A cast aluminum oil tank fed the motor, and the machine was set up for flat-road speed instead of short, violent launches up loose ground.
The details are part of what make the DAR so interesting. The motorcycle carried equipment rarely seen on a pure racing special, including a fork-mounted toolbox and a spark plug holder. In the photos, the large air-cooled spark plugs can be seen mounted just behind the handlebars along the centerline of the motorcycle. That is a small detail, but it says a lot about the difference between a European road race and an American hillclimb.
Paul Weyres had success with the DAR in Europe, including mountain-road competition. No original DAR is known in the same way the surviving DAH hillclimbers are discussed today, so the road-racing branch of this story is harder to pin down. Still, it should not be treated as a literal one-off. It was a tiny DAH-based road-racing offshoot, and that makes it one of the more unusual Harley-Davidson factory competition motorcycles of the period.
How Many DAHs Were Built, and How Many Survive?
Counting DAHs is not simple. Some sources say approximately 25 motors were built. Other summaries use a number closer to 20, while a few later descriptions push the count higher. The safest way to state it is that roughly 20 to 25 DAH machines or engines are supported by the best available evidence.
The survival count is just as tricky. A substantially complete original-pattern DAH is not the same thing as a partial machine, a later-updated racer, a restored example built around original parts, or a reconstruction based on period photos and surviving components. That is why different sources can give different numbers without necessarily talking about the exact same category of machine.
What is clear is that the DAH was never common. It was a factory racing tool built for a narrow job at a specific moment in Harley-Davidson competition history. Some examples survive in museum and collection settings, while others are known through fragments, restorations, or research into individual engine and chassis histories.
The DAH began as Harley-Davidson’s answer to a hillclimb problem, but it ended up as one of the Motor Company’s most unusual prewar racing motorcycles. It brought overhead valves, four exhaust pipes, alcohol-fueled competition tuning, chassis experimentation, and recirculating oiling into one small-batch factory program. From John Grove’s first win near Pittsburgh to Joe Petrali’s national titles and the rare DAR road-racing branch in Europe, the DAH belongs in the middle of Harley-Davidson’s early-1930s racing story.