c.1990 ADB Avenger / PBH Scott-Rotax 560cc Motocross

Offered here is a UK-built one-off motocrosser with direct Horst Leitner, ATK and PBH lineage.
Among the rarest and most unusual four-stroke motocross machines of its era, this remarkable ADB Avenger/PBH Scott represents the convergence of several influential figures and companies within the specialist off-road motorcycle industry. Its origins can be traced to the final motorcycle design work of renowned Austrian engineer and racer Horst Leitner, creator of the innovative American ATK motorcycles.

Leitner first gained recognition through his pioneering engineering concepts, including anti-chain torque systems, countershaft-mounted rear brakes, and highly distinctive chassis layouts. Following the success of ATK in the USA during the 1980s, he left the company to establish AMP Research, a design consultancy through which he continued developing innovative motorcycle concepts.

At the same time, British construction entrepreneur and motocross enthusiast Mike George sought to create a competitive British-built four-stroke moto-crosser under the PBH name. To realise this ambition, PBH commissioned AMP Research to design and construct a prototype machine. The resulting motorcycle, known as the PBH Scott, became the final dirt-bike project personally designed by Leitner. It featured a chromoly box-section frame, laid-down rear shock absorber, anti-chain tension system, and an exceptionally slim chassis design. Production numbers, however, remained extremely limited before the project was discontinued.

Following the collapse of the PBH motorcycle venture, remaining chassis and components were acquired by former ATK principal Ken Wilkes, who had established a new company, American Dirt Bike (ADB). Wilkes combined the PBH-designed frames with proven Rotax single-cylinder four-stroke engines and ATK-derived components, creating the strikingly styled ADB Avenger. Reportedly no more than ten examples were produced.

The machine offered here possesses an even more intriguing history. Research has established that it is not one of the small number of production Avengers assembled in the USA. Instead, it was constructed in Britain during the 1990s by Danny Wyse, whose family were UK importers of ATK motorcycles and had acquired the remaining stock of PBH Scott parts when the project ended. When Wilkes sought European representation for the Avenger, he supplied an Avenger conversion kit to the Wyse family, who adapted one of their original PBH Scott frames using a CCM-specification 560cc Rotax engine. The completed machine was subsequently raced by Danny's brother, Vince Wyse, in selected British four-stroke championship events.

Consequently, this motorcycle occupies a unique position in off-road racing history. Sharing the engineering DNA of both the PBH Scott prototype and the ultra-rare ADB Avenger, it is effectively a British-built one-off development machine that links two significant but short-lived chapters in specialist four-stroke motocross design. As such, it represents an exceptional opportunity for collectors of rare competition motorcycles and students of Horst Leitner's influential engineering legacy. There is a very thorough documentary regarding this motorcycle on the 999Lazer Youtube channel which is highly recommended viewing.
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