This Service Repair Manual covers Single Cylinder OHV, Air-Cooled engines, including horizontal shaft series 110000, 120000, 150000, 200000, 210000, and vertical shaft series 97700 & 99700, 110000, 120000, 210000, 280000, 310000, 330000. These engines are renowned for their robust engineering and reliable performance across a wide range of applications. This manual provides comprehensive guidance for repairs, maintenance, and servicing. It includes detailed exploded views, step-by-step procedures, pictures, and diagrams for all major engine systems, such as ignition, carburetion, governor, lubrication, starter, charging, exhaust, oil cooler, and gear reduction. Additionally, it features a maintenance schedule, troubleshooting guide, torque specifications, and instructions for speed control adjustments and fuel filter/pump service, empowering owners and technicians to maintain optimal engine function.