ATK 604 MX - Specifications & Review

Company History

ATK began with Austrian engineer and motocrosser Horst Leitner, who emigrated to the U.S. and set about solving chain-induced suspension squat and hop. His Anti-Tension Kettenantrieb (ATK) system re-routed the chain line and pivot relationships to keep the rear suspension working cleanly under power. In the 1980s–90s, ATK dirt bikes earned a cult following in America for their inventive engineering: side-mounted shock layouts, countershaft disc brakes on some models, and chassis that rewarded aggressive, technical riding. As the brand grew, production and parts support shifted within the U.S., and ATK built both two-strokes and thumping four-strokes aimed at desert racing, enduro, and cross-country. While Japanese and European giants dominated racing headlines, ATK carved space by being nimble—listening to riders, iterating quickly, and building in limited numbers for enthusiasts who valued feel and simplicity. Later, the company experimented with street-legal singles and acquired assets to produce other models domestically, keeping a boutique American off-road presence alive. Historically, ATK represents the garage-genius strand of motorcycling: an engineer sees a problem, builds a better mousetrap, and convinces riders with lap times and smiles. Owners still praise the bikes’ traction under throttle and the brand’s willingness to zig when others zagged—proof that meaningful innovation can come from small teams with a clear idea.