This manual provides comprehensive service and repair information for Mongoose 50 (KXR 50) and Mongoose 90 (KXR 90) ATVs, covering model years 2004 through 2014. A respected manufacturer of powersports vehicles, the Mongoose series was designed as sport ATVs, with these models specifically catering to younger riders. Known for their reliability and performance in their class, these ATVs feature automatic Continuously Variable Transmissions (CVT) and chain drive systems, with the 50cc and 90cc variants typically utilizing air-cooled, single-cylinder engines. The engineering quality of these ATVs is supported by detailed documentation that ensures their longevity and optimal performance for recreational riding. This factory service manual is an indispensable resource for owners and technicians alike. It details all aspects of maintenance, from regular checks and lubrication to complete disassembly and reassembly of the engine, chassis, and electrical systems. The manual includes troubleshooting guidance, diagnostic procedures, critical torque specifications, wiring schematics, and exploded diagrams, all presented with hundreds of photos and illustrations. Its exhaustive coverage ensures that users can effectively maintain, repair, and diagnose issues across all major components, from the engine and fuel system to the braking and suspension systems, making it a complete guide for ensuring the safe and efficient operation of your Mongoose ATV.