MXA’S FORGOTTEN MOTOCROSS TECH: HOW THE ATK 604 WENT TO ENGLAND & BECAME THE AVENGER

MXA test rider Willy Musgrave puts an ADB Avenger 600 through its paces.

Motocross history is filled with examples of creative ideas that were heralded as groundbreaking, but, because of the rapid rate of change in development, sank into the swamp of forgotten technology. Although some ideas are best left abandoned, others were truly innovative (if not ultimately successful). MXA loves to reveal motocross’ tech trivia.  Do you remember the ADB Avenger?

You’ll need a program to keep up with the storyline behind the Avenger motorcycle. As with all American-designed motocross bikes, it starts with Horst Leitner. The Austrian-born, but American-based, Leitner founded ATK Motorcycles in 1982, but in 1990 he left ATK to start AMP Research. ATK was taken over by Ken Wilkes, who sold the company to a Utah-based investment group, but the deal between the two went sour. While the Utah group continued to produce ATK motorcycles, Wilkes formed a new company called ADB (American Dirt Bikes), which started selling spare parts for older-model ATK’s. It was a messy situation.

The ATK 604 was a custom-built four-stroke designed for motocross and off-road. It was extremely popular.

The 1990 AMP Research 125 two-stroke that Horst Leinter designed for KTM in 1990.

Horst Leitner was commissioned to design a ready for production, prototype 600c four-stroke for the British PBH company. It was assembled in England, but sold under the name Scott.

Meanwhile, Scottish Grand Prix racer Vic Allen approached AMP Research about building him a prototype, 600cc, four-stroke, motocross bike for the British-based PBH company. AMP built PBH a prototype, which was taken to England and marketed under the name Scott. But, Scott (PBH) went bankrupt and Ken Wilkes bought their left over stockpile of AMP-designed bikes, moved them back to America and labeled them as the ADB Avenger (the Avenger name was a barbed reference to the Utah ATK group). But according to ADB, ATK pressured Rotax to cut-off ADB’s supply of engines. ADB sued, and by the time the suit was settle, the Avenger was history.

A 1996 ADB Avenger stripped of its bodywork reveals  all of the classic Horst Leitner touches; straight rectangular chromoly frame, countershaft disc brake, laid-down no-link shock and ultra-slim dimensions.n.

With the bodywork in place the ADB Avenger looked bigger and heavier than it was (note the difference to the photo above). Horst didn’t want the bodywork, but got paid to design the bike, not the cosmetics.

Are you still with us? Here is a recap. The original ATK founder sold ATK and started AMP. The new ATK owner sold ATK to a group in Utah and the old ATK became ADB. AMP designed a bike for PBH. PBH went bankrupt and sold the AMP design to ADB. ADB started production of the Avenger to get even with the new ATK. Old ATK, now ADB, sued the new ATK, plus Rotax, and by the time the dust settled only ten ADB Avengers were ever produced.

Horst always got nervous whenever Jody fired up the electric eraser over the blueprints.

As for Horst Leitner, he had no financial interest in PBH or ADB once he cashed the design check. AMP Research went on to design mountain bikes, automobile parts, Bed Extenders and for motocross, the AMP Research KTM 125 prototype for Mattighofen. Today, the ADB Avenger is kaput. ATK Utah has been sold, bought and rebought several times. And AMP Research still thrives in the automobile business. Horst, now 80, Sold AMP Research several years ago for millions and has retired to his Laguna Beach mountain top retreat.