Why This Harley Is A Collector’s Secret

If classic motorcycles had a royal family, the Knucklehead would be one of those grand uncles everyone points at and says, “There! That’s the reason motorcycling looks the way it does!” It is bulbous, unapologetically mechanical, and somehow both elegant and burly all at once. For riders and collectors who love machines that shout “engine first,” the Harley-Davidson Knucklehead (built from 1936 to 1947) is a quietly fierce trophy.

It isn’t as ostentatious as a museum piece and not as commonly discussed as later icons, but once you know it, you never forget it. Part of what makes the cruiser feel secretive is how it arrived. It came in the depths of the Great Depression and then soldiered through the war years. It wasn’t born into flash or hype. Instead, it delivered something more useful and lasting, a genuine technological leap for Harley: the company’s first production overhead-valve V-twin.

That was a big deal. Overnight (well, 1936 to be exact) Harley went from producing sturdy, dependable machines to offering much stronger performance and refinement in its big twins. Riders noticed torque, durability and a willingness to cruise at higher speeds. Builders and tinkerers, on the other hand, noticed the handsome, knuckle-shaped rocker boxes that later gave the engine its nickname.

A Little History, Without Getting Dusty

Via Chris Phutully on Flickr

In 1936, Harley-Davidson introduced the EL model with that new overhead-valve V-twin. The engine was a two-cylinder, 45-degree V with pushrod actuation and two valves per cylinder – smart, rugged and a clear step forward from the older flathead designs. Over its production run through 1947, the Knucklehead evolved (changes to displacement, carburation, gearboxes and styling happened), but the basic character remained. In 1948, the Knucklehead gave way to the Panhead, but the Knuckle’s place in Harley lore was already secured. It is both the technical pivot point from earlier Harleys and the aesthetic ancestor of every big twin that came after.

1947 Harley-Davidson EL Knucklehead Engine

Why The Knucklehead Is A Collector’s Secret

And Not Just Another Pretty Old Bike

Thesupermat via Wikimedia Commons

There are plenty of reasons Knuckleheads quietly climb in value and esteem, and most of them come back to three simple ideas: rarity, story, and mechanical charm.

• Rarity & originality: While Knuckleheads were mass-produced to the standards of the 1930s and ’40s, surviving original or correctly restored examples in good condition are relatively scarce. Time, war, and the aftermarket churn took a toll; many bikes were altered, rebuilt with later parts, or scrapped. A matching-numbers, well-provenance Knucklehead is therefore a prized find.
• Story: Each Knucklehead is a piece of American mechanical history. Depression era engineering, pre-war touring culture, wartime production impact and post-war motorcycle evolution. Collectors treasure machines with narrative, and Knuckleheads come pre-loaded with it.
• Mechanical charm: Compared with later, more complex machines, Knuckleheads are refreshingly accessible: straightforward mechanical parts, obvious engineering, and a sound and feel that screams “big twin.” That visceral connection matters to collectors who wrench as much as they display.

Put together, those factors make the Knucklehead a bike that rewards both riding and collecting. It’s not just a piece to look at on a shelf. Rather it’s something you can understand, admire and, if you like, ride.

What Made The Engine Famous

Jean-Luc 2005 via Wikimedia Commons

Mechanically, the Knucklehead was praised because it brought real horsepower and a sturdier, more modern valve train to Harley’s flagship bikes. Riders gained more usable power and a more resilient engine layout for higher mileage and heavier loads (sidecars were common then). Aesthetically, those rocker-box shapes – the “knuckles” – lent the engine a personality; before long, engine heads became a way for riders to identify a Harley at a glance. Culturally, Knuckleheads later became the raw material of the custom and chopper movements: builders loved the lines and the mechanical honesty. The combination of form and function is why the engine name stuck and why enthusiasts still talk about the Knucklehead.

1947 Harley-Davidson EL Knucklehead Chassis

Recent Auction Activity

Jean-Luc 2005 via Wikimedia Commons

If you thought Knuckleheads were only found in dusty barns or private museums, think again. Major auction houses regularly list Knuckleheads, and in recent years several examples have sold for five-figure to low six-figure prices. Auction results and listings show the market is active: Mecum has offered multiple Knuckleheads at its Las Vegas and specialty motorcycle auctions (examples from the 1930s and a 1947 EL have appeared in their 2024–2025 catalogs).

RM Sotheby’s and other major houses have also handled Knuckleheads in the past, and specialist auctions sometimes surface rare or very original examples. Recent hammer prices have ranged widely depending on originality and provenance. You’ll see numbers from roughly $100,000 up through higher figures for exceptional, first-year or concours restorations.

A Small Note On Hunting One Down At Auction

Cheesewillakers via Wikimedia Commons

If you’re tempted to chase a Knucklehead, expect two things: diligence and patience. Auctions list examples from time to time, but the important work is verification. Matching numbers, documentation, restoration history and condition are what separate a good buy from a regret. Specialist auction houses and motorcycle dealers are a better place to start than general classifieds. Also, track sale catalogs and recent results (Mecum’s Las Vegas motorcycle event and specialist motorcycle auctions are good regular places to watch). Those listings tell you not just what’s available now, but what similar bikes have sold for recently.

How To Think Like A Knucklehead Collector (Quick Checklist)

• Check matching numbers: engine and frame numbers, and documented history where possible.
• Inspect originality: is the paint era-correct? Are any prohibited “improvements” hiding under shiny chrome?
• Condition matters: a sympathetic, documented restoration that kept originality will typically beat a heavily modified “custom” for collector value.
• Provenance sells: bikes with famous previous owners, race history, or museum display records command premiums.
• Expect variability: prices depend heavily on year (1936 first-year machines attract a premium), originality and how “complete” the bike is.

Why The Knucklehead Stays Special

Michael Barera via Wikimedia Commons

There’s a quiet satisfaction in owning something that shaped an industry. The Knucklehead isn’t just an old Harley; it’s the machine that nudged Harley-Davidson into the modern big-twin era. It has the right mix of mechanical significance, visual charisma, and scarcity to be desirable, but it’s not so famous that everybody already owns one. That half-hidden status is what makes it a collector’s secret: once you know it, you want to tell your friends, but you also secretly hope fewer people do.