Experimental “Mini Knuck” – 1938/39 Harley-Davidson XE-4

In America, Cruiser, Vintage by Tim HuberLeave a Comment

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8-28-19 Update: Well, it looks like this bike has sold, as it’s now on the other side of the country…and the BIN is up by over $50K. Find it for sale in Newtown, Pennsylvania with a BIN of $250,000 .


Post Listing Update: This prototype Harley did not get any interest at the BIN of $195,000.


Despite a global financial crisis greatly limiting available funds and resources at the start of the 1930’s, Harley-Davidson nonetheless managed to develop a number of significant models, including the Knucklehead, which debuted in 1936.

Starting in ‘31, Harley’s higher-ups green-lit a 61ci pushrod-and-rocker overhead valve power plant. The new Harley would also feature a pumped, recirculating oil system — a marked improvement over the total-loss systems that were the norm during this era. The flow paths of the exhaust and intake were also greatly improved, which, when combined with the aforementioned improved heat management and oil circulation system, afforded the Harley damn near twice the oomph of previous gen offerings from the Bar and Shield brand.

Unfortunately not all of the proposed ideas coming out of the Milwaukee factory were winners. One of these experimental Harleys was a 52ci overhead-valve (OHV) runner, supposedly designed by none other than William Harley himself. This machine was reportedly one of five (2nd gen) protobikes that left the factory, however this specimen is said to be the only one with aluminum heads and barrels.

The seller also goes on to state, “The motor is proprietary to this machine using narrow cams and oversized cam cover. With an A-frame-style head, motor no. 4 is marked ‘EX’”. The ad also claims this example sports a domed pistons as well as one-off narrow stepped hubs and small spoke rims.

Though this example was supposedly designed and owned by Bill Harley, it later ended up in the hands of Roy Egeberg who supposedly purchased it from the factory, presumably along with a heap of spares. Egeberg — who registered this bike in Minnesota— sold this experimental scoot in 1974 to renowned vintage Harley expert, Daniel Pugens. More recently this example underwent a complete restoration, reportedly using “parts purchased from Egeberg”.

With examples like this, proving authenticity is key. Regarding this, the seller says, “the authenticity of this particular prototype experimental motorcycle is well documented including in the Harley-Davidson archives, extensively in Herb Wagner’s Harley-Davidson 1930-1941, and in Jerry Hatfield’s Inside Harley-Davidson.”

The seller points out that this is almost certainly the only existing example of its kind. Add to that the fact it previously belonged to William Harley himself and you can start to get a sense of the significance of this machine. For a more in-depth look at the history and development of the Knucklehead, I highly recommend this writeup Kevin Cameron did for Cycle World.

You can find this Ex-Bill Harley 1938/39 Harley-Davidson XE-4 experimental prototype for sale in Costa Mesa, California with a BIN price of $195,000 or best offer

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