The Flathead, an undeserved underdog

Text by Uwe Ehinger
Studio photo : Benoit Guerry
Motor Photo by Hermann Köpf
others courtesy of Ehinger Kraftrad

As a builder and collector of custom bikes, I love engines so much that I really have a hard time resisting the urge to philosophize about design details like oil pumps and compression ratios for hours on end. Although it’s actually quite easy to explain my fascination with one of the probably most formative machines of the 1930’s and 40’s.

One reason is Harley Davidson. Because although this brand produced a larger number of Flatheads, their Knuckleheads were significantly more popular. This is partly attributable to their sportier performance, but it was also due to the emerging rocker scene in the 1960’s and their portrayal in movies like “Easy Rider”. This created a hype about Knuckleheads and Panheads that persists to this day. And just like everything that’s “cult”, it has little to do with quality or rational thinking. Although the Flatheads manufactured from 1937 to 1948 by brands like Indian, BMW and Brough Superior were technically simpler, they were a lot more robust than over head valves (OHV) engines.

These engines not only made do with less wearing parts, they usually had a larger engine capacity, too. This caught the attention of public authorities such as the police and the army, which both had a preference for Flatheads in the 30’s and 40’s. When Harley offered the New York Police Department around 250 bikes for free, the police only went for the deal once they had been assured that the bikes would be delivered with an Indian red paint finish, the Indian right-hand shift and a Bosch magneto ignition. They were thus given the model name: “UMG” for magneto generated.

Another advantage of these engines, especially for collectors, is their versatility. There are an abundance of different models – such as U, UL, UH, ULH, UMG, UA and UN – and much fewer of them were manufactured than some of the Knucklehead models. There are so many versions of Flatheads; even a Navy edition consisting of just 10 bikes, which were only used in parades. If anyone happens to have one of these at home, I recommend that you relocate your domicile to a bank vault.

But the most impressive thing about the Flathead is its sound. It’s indescribable! Let me try: a hungry T-Rex with a filthy temper. Trapped in the Royal Concert Hall. Deep, rumbling and forceful. Because unlike the Knucklehead, the Flathead doesn’t require a rattling rocker arm in the cylinder head.

The Flathead comes with so many inspiring characteristics for motorcycle enthusiasts that it is easily the most underestimated engine type in the world. This turns it into a furious underdog, an outlaw in the shadow of the famous Knucklehead. But didn’t it all begin with outsiders?

This 41 UL was restored by Francis Villedon @ Milwaukee Belle for Fabrice Roux, The motor was rebuilt byAlain Servie

More U models by Ehinger Kraftrad