Scavenger Hunt: 1936 Harley-Davidson EL

Then there are those such as Paul Woelbing of Franklin, Wisconsin, who would choose to piece together, part by part, a rare 1936 Harley-Davidson EL, a model introduced mid-year in the Motor Company’s production run, and one with more than 155 changes in the first six months of its release.

The pair met in the mid-1990s when Paul bought his first old motorcycle from Mark, a 1948 Indian Chief. A 1949 Harley-Davidson Panhead followed the Indian into Paul’s garage, and it wasn’t long before he realized he was amassing a small collection of interesting motorcycles. As part of his nascent motorcycle education, Paul and Mark made annual pilgrimages to many of the antique motorcycle swap meets, including those in Wauseon, Ohio; Davenport, Iowa; and Farmington, Minnesota.

“After I’d met him, Mark really took an interest in 1930s Harley-Davidsons,” Paul explains. “And, he took a particular interest in the 1936 Knucklehead as a noteworthy machine.”

The Knucklehead, so-called because the rocker covers atop the V-twin cylinders slightly resemble two knuckles on a clenched fist, was Harley-Davidson’s first full-production overhead-valve V-twin engine. Prior to this, the only overhead-valve V-twin built by the Motor Company was a specialized piece of equipment constructed for racing, and on a very limited basis. In 1926, Harley-Davidson did offer a 21-cubic-inch single-cylinder machine called the BA, better known by its nickname, the Peashooter, that was available as a flathead or with an overhead-valve layout.

For their bread-and-butter large-capacity V-twins, though, Harley-Davidson relied on sidevalve, or flathead, engine technology. By the late 1920s H-D customers riding the larger twins were demanding more power and according to well-known motor-journalist Kevin Cameron, the cast-iron sidevalve cylinders of these engines wouldn’t readily accommodate the request.

“The enduring problem of the sidevalve engine is that its very hot-running exhaust valve seat and exhaust port must be cast as part of the cylinder casting itself,” Cameron wrote in an online Cycle World column about the advent of the Knucklehead engine. “The more power such engines made, the hotter these parts became, distorting the cylinder out of round and making oil control and combustion gas sealing difficult.”

In order to offer the sporting rider a faster mount, in 1931 Harley-Davidson engineers were tasked with developing an overhead-valve V-twin engine that could be put into regular production. The rockers would be operated by pushrods, and the two valves — one intake, one exhaust per cylinder — situated in a cast-iron head with plenty of fins to better channel cooling air over the hottest areas.

Further adding to the design brief, overhead valves required a recirculating oil system, with a pump and separate tank, to ensure sufficient lubrication would reach the valve gear. For comparison, traditional sidevalve engines were most often lubricated by total-loss systems. On the older Harley-Davidson sidevalve engines, for example, oil was gravity-fed from the tank (part of one side of the gas tank, where it was separated by a double-skinned steel wall) to a pump on the cam cover. From there, oil was distributed throughout the engine and was not pumped back to the tank. Instead, the oil would eventually leak past piston rings to burn in the combustion process or otherwise seep out between castings — total-loss.

Bad news

Worldwide economic difficulties of the Depression, however, were taking their toll on Harley-Davidson — from sales of 22,350 motorcycles in 1928 to 3,703 in 1933. Regardless, the Motor Company carried on funding development of the new overhead-valve engine with dry-sump lubrication. For this new recirculating system, a double gear oil pump found a home at the rear of the aluminum crankcase and from a separate tank, fed lubricant under pressure to the critical internal components, including the overhead valve train. Meanwhile, the scavenge side of the pump returned hot oil from the crankcase back to the tank, where the process would simply start over.

As first designed and tested late in 1933 and through 1934 and ’35, the new overhead-valve engine did not feature return oil lines from the rockerboxes. Plus, the ‘boxes were open, without a sealed cover, so that oil would leak out copiously. Harley-Davidson tried to better meter the flow of oil to the valve train, without success. But that didn’t stop Harley-Davidson from debuting the overhead-valve machine at a dealer meeting in late November 1935 at the Schroeder Hotel in Milwaukee, Wisconsin.

“I think Harley-Davidson was fairly nervous about the launch,” Paul explains. “I’ve seen a photograph of that meeting, and that overhead-valve motorcycle is not the highlight in the room.”

By the time Harley-Davidson officially launched the overhead-valve model in 1936, the oil issue had been somewhat, but not completely, rectified. Two small caps on each rocker cover now protected the valve stems. Kevin Cameron notes, though, “Much of the reason for this chronic leakage was the complex shape of the surfaces to be sealed, which were over-ambitious. When heads heat up and cool down, gaskets are subjected to expansion and contraction of the parts they seal, and this remains a difficult problem to this day.”

The machine was available as the lower 6:1 compression ratio model E, good for approximately 37 horsepower, and the sportier 7:1 compression model EL that made 40 horsepower, both at 4,800rpm. Bore and stroke of the 61-cubic-inch engine was 3-5/16-inches by 3-1/2-inches, and the cast-iron cylinders were each secured to the crankcases via four bolts. The crankshaft rotated on roller main bearings and the two 8.125-inch-diameter cast-iron flywheels sandwiched fork-and-blade
connecting rods that turned on caged 1/4-inch roller bearings on a 1.125-inch steel crankpin. A four-lobe cam, located on the right side of the engine, operated four separate pushrods to motivate the rockers and overhead valves.

Power pulses were transferred to a new 4-speed constant-mesh transmission through a redesigned multi-plate clutch, while a new single-butted double downtube frame and a twin-leg springer fork constructed of smooth, extruded tubing were also introduced. Overall, the new motorcycle — with fluids — weighed in at 565 pounds.

While beautifully and dramatically styled in the Art-Deco sensibility of the era and strong-running, the freshly released overhead-valve Harley-Davidsons were far from perfect. This was a design process Paul refers to as, clearly tongue-in-cheek, “release and develop.”

Noted Knucklehead restorer Matt Olsen of Carl’s Cycle Supply in Aberdeen, South Dakota, says Harley-Davidson produced just over 1,700 examples of the E and EL in 1936. As Paul alluded to earlier, there were many revisions made to bring the machine up to a satisfactory standard during the first year of its production run. On-the-fly changes include the fitting of three different types of timing covers and two kickstarter gearing ratios while the ignition timing was also altered. Oil tanks and lines were changed seven times, there were modifications to valve springs, rocker oil feed and improved rockers themselves, and five different frame alterations.

Over the next few years, Harley-Davidson dialed in the overhead-valve motorcycle and while sales numbers weren’t particularly strong, it eventually became a popular-selling model for the company. In 1941, engine capacity was increased to 74 cubic inches to create the FL, and after the war, sales figures of the larger model surged. The last year of the Knucklehead was 1947, as Harley-Davidson released a new, aluminum-head model that fall.

When that machine was released, V-twin enthusiasts dubbed it the “Panhead” thanks to what looked like upside-down cake pan rocker covers. After that, the earlier overhead-valve model was nicknamed the Knucklehead — and the names stuck.

Build beginnings

It wasn’t too difficult for Paul to become interested in Mark’s passion for the early Knucklehead models, and when the pair located a 1936 EL frame and engine, Paul bought the parts as the basis for a complete build. This happened in 1998, back when eBay was just emerging. A few components were purchased through the online auction site, but several important pieces were sourced from the late Clete Borchert of Old Dude Vintage Parts & Service. The shop, located in Lilburn, Georgia, is now owned and operated by Clete’s son, Bart.

“The way you restore one of these early Knuckleheads is by the serial number of the engine, as that will indicate early, mid or late production through 1936,” Paul explains. “The engine number on what I had fell into a mid-production period, and you do your best to guess what changes occurred and when.”

Harley-Davidson did not stamp date codes on their cast components until late in 1938, and frame serial numbers were not marked until 1970. That means Paul and Mark played the role of detectives and searched for four years to locate all factory-correct parts based, for the most part, on visual clues.

They were lucky to find a transmission that would have been originally built midway through the first year of production. And for 1936 and 1937, both front and rear fenders featured a butterfly clip to retain the mounting braces, and a set was found at a swap meet.

The engine and transmission were rebuilt by the late Ken Presson of The Motor Company in Davenport, Iowa, using all original parts. “Kenny died in 2011,” Paul says. “But back in the 1970s, he got to be friends with a guy who’d had a Harley dealership in the 1930s and Kenny eventually bought out tons of new-old-stock components at a time when nobody was putting much value on the old parts.”

Throughout the restoration, it was Mark’s academic approach that appealed to Paul. Whenever possible, Mark would find an original Knucklehead and do only what was necessary to make it run. But, if a bike was too far gone, he’d restore it, correctly, right down to the last detail.

“Mark really studied the bikes, and in an obsessive way,” Paul says. “For example, Mark would look and see runs in the factory-applied paint indicating that these parts were dip painted, so he’d replicate the painting process, leaving the runs. He also made canvas covers to keep the white rubber of the grips clean, just like Harley did.”

For 1936, the EL could be bought in two-tone paint jobs including Sherwood Green with Silver, Teak Red with Black, Dusk Gray with Royal Buff, Venetian Blue with Croydon Cream, and Nile Green with Maroon. It was the last combination that Paul originally wanted to use, but finally decided to finish it in the Dusk Gray and Royal Buff colors. After an original seat pan was restored, it was covered in fresh leather by Howard Heilman.

With the Knucklehead finished in 2003, the bike has since been sitting in Paul’s office. He has several other classic machines that see regular use, however, he’s decided 2021 will be the year the ’36 EL finally sees the road. “Because it’s not really ever been broken in, and because it’s been sitting, I think it needs a good recommissioning,” Paul says of the motorcycle. To that end, Matt Olsen, who specializes not only in Knuckleheads but also Panheads with his dad, Carl, at Carl’s Cycle Supply, is planning on picking the bike up later in 2019.

That’ll give everyone enough time to ensure that this Knucklehead — built the hard way, finding piece after piece at swap meets like some kind of mechanical scavenger hunt — is ready to roll for its 85th birthday. MC