When it comes to rare motorcycles, nothing quite matches the mystique of the E90 AJS Porcupine. Built in the late 1940s by Associated Motor Cycles (AMC) in Britain, the Porcupine wasn’t just a motorcycle—it was a revolutionary racing machine that would go on to make history in the world of Grand Prix racing. With only four units ever produced, it remains one of the most coveted collector’s motorcycles in the world.
The Birth of the Porcupine
The story begins in 1945, just after World War II, when AJS set out to create a groundbreaking racing motorcycle to dominate the 500cc Grand Prix class. The E90 was unlike anything seen before—it featured a 500cc DOHC twin-cylinder engine, horizontally mounted to lower the center of gravity and improve aerodynamics. Its unusual finned cylinder heads, which helped with cooling, earned it the nickname “Porcupine”.
Why It Was So Special
At a time when most racing bikes were air-cooled singles, the E90 Porcupine brought innovation and sophistication:
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Horizontally mounted cylinders – improved handling and weight distribution.
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Unique aluminum alloy engine – reduced weight without sacrificing strength.
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Exposed cooling fins – enhanced airflow, hence the “Porcupine” look.
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Magneto ignition & advanced carburetors – for higher performance on the track.
Racing Glory
The Porcupine achieved its most famous victory in 1949, when rider Les Graham won the inaugural 500cc World Championship. This made the E90 the only twin-cylinder motorcycle to ever win a 500cc GP World Championship title. However, despite its potential, mechanical issues and limited production meant its racing career was short-lived.
Rarity and Value
With only four E90 Porcupines ever built, each surviving example is a priceless piece of motorcycle history. In 2011, one was sold at auction for a staggering $675,000, cementing its place among the most valuable motorcycles ever sold.
Legacy of the Porcupine
Today, the E90 AJS Porcupine stands as a symbol of post-war engineering ambition and racing innovation. It’s a reminder of a golden era when motorcycle designers dared to break all the rules. Owning one isn’t just about collecting—it’s about preserving a piece of motorsport history that will never be repeated.
The E90 AJS Porcupine is not just a motorcycle—it’s a masterpiece of engineering and rarity. For collectors and enthusiasts, it represents the ultimate blend of performance, innovation, and history. In the world of classic bikes, nothing else comes close to its legendary status.
