Not Just a Knucklehead: The 1936 Model EL

The first new motorcycle of the Great Depression was a bit of a gamble for Harley-Davidson. Introducing what would eventually be known as the "knucklehead" engine, the 1936 EL was a pivotal model that continues to influence H-D® motorcycles today.

By Harley-Davidson Museum

Following the stock market crash of 1929, the business world ground nearly to a halt.

The motorcycle industry was hit hard by the Great Depression. By 1933, overall motorcycle sales in the US had reached an historic low, still unmatched to present day. Some motorcycle manufacturers closed their doors. Others were able to stay afloat, but any profits made had to be invested wisely. While Harley-Davidson® motorcycle customers and dealers looked forward to the next new model, the Motor Company knew any new motorcycle was going to be a risk.

Joe Petrali and Crowd (1937-03)Harley-Davidson Museum

A Risky New Idea

Co-founder and Chief Engineer William Harley headed new product development. As part of the Board of Directors, he led conversations about innovative product ideas. Among these ideas was a twin cylinder motorcycle unlike any other Harley-Davidson had previously sold.

Harley-Davidson® 1936 model EL (1936) by Harley-Davidson Motor CompanyHarley-Davidson Museum

Harley convinced the Board to give it a shot. 

But mere months before its launch, they still debated whether the motorcycle should even be built. 

Harley-Davidson® EL Model (1936) by Harley-Davidson Motor CompanyHarley-Davidson Museum

They knew it was a risk but were also excited about its possibilities. 

Informally dubbed the “61” for its cubic inch displacement, the all-new model was approved. It was first available in 1936.

The founders inspect their newest model (1935)Harley-Davidson Museum

The founders of Harley-Davidson inspect an early 1936 "61" coming from the assembly line. Left to Right are Arthur Davidson, Walter Davidson, William S. Harley and William A. Davidson.

The motorcycle would go on to define Harley-Davidson’s future.

1936 model "61" engine detail (1936) by Harley-Davidson Motor CompanyHarley-Davidson Museum

Origin of the "Knucklehead" Engine

Decades after release, motorcyclists began to give nicknames to Harley-Davidson® engines. Prior to the "61", a side-valve engine called a "flathead" had been powering riders through thick and thin. 

The “61” featured a new engine and transmission. With its overhead valves, it offered more power. It was eventually nicknamed the "Knucklehead" due to its resemblance to a clenched fist.

Petrali on record-breaking motorcycle (1937)Harley-Davidson Museum

The engine power needed to be proven, not merely mentioned.

A key way to show automotive power was by breaking land speed records.  Harley-Davidson brought a highly modified "61" to Daytona Beach to do just that. The distinctive streamliner was piloted by Joe Petrali, one of the best motorcycle racers of the day. 

Poster announcing new land speed record (1937) by Harley-Davidson Motor CompanyHarley-Davidson Museum

They succeeded, with Joe achieving a blistering 136 miles per hour. 

"Even above the steady roar of the surf, you could hear the deep pitched drone of the 61," wrote John Balmer in Harley-Davidson Enthusiast ™ magazine. 

Joe Petrali and Crowd (1937-03)Harley-Davidson Museum

"When Petrali came back the photographers started their work and congratulations flew thick and fast. A curious crowd edged around to see the famous blue 61 OHV. Everybody had big, happy grins and well they might—hadn't they just seen an afternoon of record breaking performances?” – The Motorcyclist, April 1937

Harley-Davidson™ EL Factory Streamliner (1936) by Harley-Davidson Motor CompanyHarley-Davidson Museum

On one of Joe's earlier runs down the beach, while going about 124 m.p.h., the front wheel had lifted off the ground. Joe said it felt like the bike was starting to fly. For a safer ride, he had the streamlined tail removed—including on the record-making run.

Rider posing on 1936 "61" motorcycle (1936)Harley-Davidson Museum

The Legacy of the "61"

The “61” was far more powerful than preceding Harley-Davidson® motorcycles. But what else did it do for motorcycling? 

Harley-Davidson® EL Model (1936) by Harley-Davidson Motor CompanyHarley-Davidson Museum

The engine architecture is still found in many of today’s H-D® motorcycles. They retained elements of the engine design and frame geometry, while also adding adaptability to future models. 

Rider Posing with Accessorized "61" (1938)Harley-Davidson Museum

No one could have predicted it, but the “61” would evolve into today’s Harley-Davidson® cruising and touring models. These motorcycles—“cruising” meaning shorter distance and “touring” for longer duration and distance with more luggage—trace their lineage back to the original “61” through their frame geometry and engine design.

Successive years and new models brought even more adaptability, and accessories to improve comfort and touring were designed for specific vehicles.

Every part of the motorcycle would be improved upon over time, but the modern descendants of the EL owe their design to the 1936 motorcycle.

Scroll through the following gallery of bikes to see some of the descendants of the legendary "61."

Harley-Davidson® 1949 model FL (1949) by Harley-Davidson Motor CompanyHarley-Davidson Museum

1949 model FL

Harley-Davidson® 1958 FL Duo Glide (1958) by Harley-Davidson Motor CompanyHarley-Davidson Museum

1958 FL Duo Glide

Harley-Davidson® 1965 Electra Glide (1965) by Harley-Davidson Motor CompanyHarley-Davidson Museum

1965 Electra Glide

Harley-Davidson® 1977 FXS Low Rider® (1977) by Harley-Davidson Motor CompanyHarley-Davidson Museum

1977 FXS Low Rider®

Harley-Davidson® 1986 FLST Heritage Softail® (1986) by Harley-Davidson Motor CompanyHarley-Davidson Museum

1986 FLST Heritage Softail®

Harley-Davidson® 1990 FLSTF Fat Boy® (1990) by Harley-Davidson Motor CompanyHarley-Davidson Museum

1990 FLSTF Fat Boy®

Harley-Davidson® 2003 100th Anniversary FLHTCUI Electra Glide® Ultra Classic® (2003) by Harley-Davidson Motor CompanyHarley-Davidson Museum

2003 100th Anniversary FLHTCUI Electra Glide

Harley-Davidson® 2018 Softail Slim® (2018) by Harley-Davidson Motor CompanyHarley-Davidson Museum

2018 Softail Slim®

Hill Climber statue (2008) by Jeff DeckerHarley-Davidson Museum

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Harley-Davidson Museum
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