History And Mystery Of The Harley Davidson EL Knucklehead

Summary

• The Knucklehead, an iconic Harley-Davidson model, boasts nostalgic charm and symbolizes the brand’s triumph over Indian Motorcycles in the 1930s.
• The innovative Knucklehead engine, featuring overhead valves, marked a turning point for H-D, pushing the company to refine and improve its design.
• Despite early technical issues, Harley-Davidson engineers worked tirelessly to enhance the Knucklehead, solidifying its status as a legendary motorcycle.

To the average person, the word “Knucklehead” is used as an insult to someone who is either clueless or foolish. But for Harley-Davidson lovers, the word will instantly bring a huge smile to their faces. This is, of course, due to the Knucklehead being one of the manufacturer’s most legendary motorcycles ever produced in its over 120-year history. Not only do they conjure up some powerful feelings of nostalgia from 1930s Americana, but they also serve as a reminder of the motorcycle that helped cook its rival competitor, Indian, into submission.

The Knucklehead, officially known as the 1936 E/ES/EL, was the first Harley-Davidson to feature overhead valves, whose valve covers resembled the knuckles on a closed fist (hence the name). In production from 1936 to 1947, it is estimated that only 41,000 Knuckleheads were made. Though the motorcycle wasn’t 100% perfect upon its debut, Harley-Davidson proceeded to refine and polish the Knucklehead into the iconic status that it holds today.

The Knucklehead Engine Put Harley-Davidson Back in the Lead

By the mid-1930s, Harley-Davidson was already established as one of the top motorcycle manufacturers in America. Both through its rapidly growing customer base, and government contracts to produce motorcycles for the US military. But despite all that, it was still chasing the tail of its arch-rival, Indian Motorcycles.

Sales were lagging behind, and the executives at Harley-Davidson needed something to boost sales and put them back in the front of the pack. Thus came the Knucklehead engine–the brand’s first V-Twin with overhead valves. The project was led by engineers Hank Syvertson and Joe Petrali, who developed Harley-Davidson’s first engine with a staggering 61 cubic inches. The only major drawback the company faced was that they had to release the engine to the public before it was completely finished.

It Marked a Turning Point For Harley-Davidson

Like the saying goes “pressure makes diamonds.”, the same can be said for how Harley-Davidson developed the Knucklehead engine. With Indian Motorcycles reigning over Harley in the 1930s, the company’s push for bigger sales led to the conception, and then production of the Knucklehead engine. Prior to its development, H-D bikes were powered by the 45 cubic inch Flathead engine, which earned its name due to its flat-topped, vented cylinder heads.

But the pressure on Harley really set in 1930 when Indian debuted with a Big Twin engine of its own, the 74 cubic inch mill. Then in 1936, the Knucklehead arrived on the scene, available in two different displacements: 61 cubic inches and 74 cubic inches. In addition to being the first Harley Big Twin to feature overhead valves, it came equipped with an effective oil circulation system to keep all of its inner workings well lubricated.

1947 Harley-Davidson EL Knucklehead Engine

The Early Knuckleheads Had Some Technical Issues

With time and pressure up against Harley-Davidson to overtake Indian, some of that made its way into some of the early versions of the Knucklehead suffering from a series of technical issues. With only 2,000 units produced in 1936, some issues that plagued this bike included brittle valve springs, rockers that were not sufficiently lubricated, and frequent instances of leaking oil. Because this was the first version of the Knucklehead engine mass-produced for the public, its shape and configuration were also drastically more complex than its predecessor. The result was a new V-Twin that had some sealing difficulties.

Harley-Davidson Engineers Made Some Much-Needed Improvements to the Newer Knuckleheads

Well aware of the technical issues hurting the first line of Knuckleheads, Harley engineers went right to work on fixing these problems and refining the development of the engine. Nearly redesigning it entirely, the engine received several enhancements, such as stiffer valve springs, an improved rocker design, a larger flywheel, and a solution for those annoying oil leaks. In addition, the company sent repair kits to Harley-Davidson dealerships to repair the motorcycles that were already sold and on the road.

By 1938, Harley had ironed out all the technical flaws but continued to improve upon the Knucklehead’s design up until its final year of production (1947). Post which, it would be replaced by its successor, the Panhead. Given that many of the parts on the original 1936 Knucklehead bikes were made that year, it is practically impossible to find replacement parts today. Restoration enthusiasts will either have to craft those specific parts themselves or alter a similar part from a separate motorcycle in order for it to work.

80 Years Later, The Harley-Davidson Knucklehead Remains an Icon

Though there were a few hiccups at the beginning, the adjustments made to the Knucklehead helped solidify it as one of the most legendary motorcycles ever produced by Harley-Davidson. Ask any H-D fanboys what model motorcycle they would want out of the brand’s entire 120+ year history, and the Knucklehead will be close to the top of the list. The unforgettable experience of riding this ultimate old-school bike, as well as the feelings of nostalgia that come with it, remind modern riders of the thrills felt when this first arrived in the mid-1930s.

With both power and speed at its disposal, it is easy to understand how the Knucklehead put Harley-Davidson back in the lead and Indian in its dust. Not to mention, how the Knucklehead engine became grounded as the foundation that all future Big V-Twin motors were built. This also resulted in the Milwaukee-Eights and Revolution engines that we enjoy today.

1947 Harley-Davidson EL Knucklehead Specifications

Modern-Day Reverence

Many new-generation Harley-Davidson riders are enthralled by the brand’s influx of high-performance bikes such as the Sportster S, Low Rider ST, Pan America 1250, Road Glide, and Street Glide. But more seasoned riders still express appreciation for the historical significance behind the Knucklehead. Much in the same way car guys would adore and appreciate a ’69 Plymouth Roadrunner.

Sure, they are not exactly everywhere on the road. But when one shows up at a motorcycle meet, it is impossible to ignore it. According to data conducted by Hagerty, the Knucklehead is more likely to appeal to Millennials or Gen Z than an Indian Chief owner. They are also four out of five times more likely to quote a Knucklehead at a higher value than boomers. Not to mention, the Knucklehead received a special shout-out from actor Jason Momoa in his Harley-Davidson x On The Roam collaboration. In addition to being the dream project for many restoration enthusiasts, the rare experience of riding around on a Knucklehead is a once-in-a-lifetime opportunity any Harley fan would be foolish to pass up.