This manual provides comprehensive service and repair information for the Knucklehead motorcycle, covering model years 1940 through 1947. Renowned for its distinctive overhead valve (OHV) or flathead V-twin engine design, the Knucklehead represents a significant era in American motorcycle engineering. These iconic machines, available in various engine configurations including the 61 cubic inch (1000cc) and 74 cubic inch (1200cc) variants, are celebrated for their robust construction and historical importance. This manual is an essential resource for owners and enthusiasts dedicated to maintaining, restoring, or rebuilding these classic models, ensuring their continued performance and heritage.

The scope of this Service Repair Workshop Manual is extensive, offering detailed guidance on all major systems of the Knucklehead. It covers in-depth procedures for engine service, transmission overhaul, fuel system maintenance, ignition system tuning, and electrical system troubleshooting. Additionally, the manual provides instructions for chassis and frame work, suspension servicing, brake system repair, and bodywork adjustments. With a strong emphasis on diagnostic procedures and detailed instructions for routine maintenance and complex rebuilds, this manual is designed to empower owners and technicians alike to perform high-quality repairs and ensure the longevity of their vintage Knucklehead motorcycles.