This manual covers the KX85 and KX100, renowned 2-stroke motocross motorcycles produced between 2001 and 2010. These bikes are engineered for peak performance in competitive off-road riding, featuring a potent 2-stroke, liquid-cooled engine equipped with an Integrated Power Valve System for an optimized powerband. The KX85, with its 84 cc displacement, and the KX100, at 99 cc, offer agile handling and robust power delivery, making them popular choices for aspiring motocross racers and performance-oriented riders. Their design prioritizes durability and responsiveness, reflecting an extensive heritage in motocross racing. This Workshop Service Manual (WSM) provides comprehensive technical information essential for the maintenance, repair, and overhaul of your KX85 or KX100. It details procedures for all major systems, including the engine, fuel, ignition, transmission, chassis, suspension, braking, and electrical systems. Within its pages, you will find step-by-step instructions for routine maintenance, detailed component disassembly and reassembly, troubleshooting guides for common issues, and precise technical specifications. This manual is an indispensable resource for owners and technicians seeking to ensure their motorcycles remain in optimal condition and perform at their best.