This manual covers the Mongoose 50 and Mongoose 90 All-Terrain Vehicles (ATVs). These ATVs, popular in the youth recreational market, are designed as entry-level off-road vehicles, offering a foundational experience for young riders. They feature reliable, air-cooled, four-stroke engines with displacements of approximately 49.5cc for the Mongoose 50 and 89cc for the Mongoose 90, both utilizing carburetor fuel delivery and CDI ignition systems. Engineered for durability and ease of use, these ATVs are equipped with automatic CVT transmissions and are intended for recreational purposes, with safety features such as adjustable throttle limiters. This comprehensive Service Repair Manual provides detailed guidance for the maintenance, troubleshooting, and repair of your Mongoose 50/90 ATV. It includes complete engine overhaul procedures, CVT and drivetrain service, fuel system maintenance, electrical system diagnostics with wiring diagrams, brake system repairs, and suspension and steering adjustments. The manual also covers routine maintenance schedules, component rebuilds, and specific technical data including torque specifications and fluid recommendations. This resource is designed to assist enthusiast owners, independent repair shops, and service technicians in effectively maintaining and repairing these ATVs, ensuring optimal performance and longevity.