ATK is an off-road motorcycle manufacturer in Utah, USA, founded by an Austrian engineer, Horst Leitner, in 1980. The name "ATK" is the abreviation of the device which Leitner patented in order to eliminate chain torque for a better handling. The device was called Anti Tension Kettenantreib, from the German "chain drive". Horst Leitner, the former 500GP racer, is well known as he designed the ATK 560, ATK 640, ATK 407 in the 80's and the Horst link design, considered an important suspension system, at the beginning of the 90's. The Horst Link is a set of rear pivots located on the chainstay just below and in front of the rear drop-out. {ad}

　　Horst sold ATK in the 90's and started AMP Research, which was the official supplier of car, truck and accessory products to original equipment manufacturers as Ford, Nissan, Mazda, Mitsubishi or Subaruso. This suspension design element was found on Horst's line of AMP bikes. In the late 90’s, the engineer sold the Horst link to Specialized Bicycles.

　　450 XC, one of the ATK bikes, has a 446cc engine which develops 46 HP at 11500 rpm. Released in 2006, it has fuel injection and electric start, Ohlins suspensions and off-road tires. The bike is not heavy at all, with only 242 lbs with only 2.6 gallons of fuel in the tank.

　　Just like its close relative, the 450XC, the MX version has a 446cc, liquid cooled, single cylinder engine which unleashes 46HP at 11500 rpm. ATK company dressed it up with Ohlins suspension, electric start and aluminium twin spare frame.

　　After the ATK 700 appeared a lot of trial addicted bikers considered that the XR650R from Honda is no longer the baddest dirt bike in the world. The XR650R has won every Baja 1000, 500 and San Felipe 250 it has ever entered.

　　In 2003, ATK purchased the remaining inventory of Cannondale Motorsports, which made it possible to add ATVs to their product line. A year later, ATK took first place in the Grand National Cross Country Championship and two Canadian National championships.

　　Currently, ATK is the only remaining off-road motorcycle manufacturer in the United States.