This manual covers the KX125 and KX250 motorcycles from the 1999 to 2002 model years. These performance-oriented two-stroke machines are renowned for their competitive edge in motocross and off-road racing, building on a strong heritage in the sport. Engineered for aggressive power delivery and agile handling, the KX series of this era featured advanced technologies such as the Integrated Power Valve System (KIPS) to optimize engine performance across the RPM range. They are characterized by their robust perimeter frames, potent single-cylinder engines, and reliable suspension systems, making them a favored choice for serious riders. The purpose of this comprehensive Workshop Service Repair Manual is to provide detailed guidance for the maintenance, troubleshooting, and repair of your KX125 or KX250. It encompasses a wide array of essential information, including general specifications, periodic maintenance schedules, and in-depth procedures for all major systems. Key areas covered include the fuel, cooling, lubrication, and electrical systems, as well as the engine top end, clutch, transmission, wheels, brakes, suspension, and frame. This manual is an invaluable resource for owners, mechanics, and technicians seeking to ensure the optimal performance and longevity of these high-performance motorcycles through accurate and detailed technical instructions.