This comprehensive service repair manual covers Harley Davidson Knucklehead and Flathead models from 1940 to 1947. It offers detailed instructions with clear illustrations, guiding you through every step of servicing, repairing, restoring, maintaining, rebuilding, and diagnosing your motorcycle. The manual covers Harley Davidson O.H.V. and Side Valve Models from 1940-1947 and provides general guidance for Big Twin Models dating back to 1937. It's packed with information on troubleshooting, and equips you with the knowledge to address any issues quickly and effectively. This manual is the same one used by professional technicians, mechanics, and workshops, making it a perfect resource for DIY enthusiasts. It provides complete step-by-step information on servicing, repairing, and preventative maintenance, serving as your essential guide through every repair and troubleshooting procedure. This manual is the ultimate resource for anyone looking to keep their classic Harley Davidson running smoothly.

The Harley-Davidson Knucklehead, produced from 1936 to 1947, marked a significant departure from the previous Flathead engine design, bringing a new level of performance and sophistication to the American motorcycle scene. This revolutionary engine, known for its distinctive "knuckles" surrounding its rocker boxes, was the first mass-produced motorcycle engine to feature overhead valves. This innovation allowed for higher compression ratios and a more efficient combustion process, resulting in a substantial power increase over the Flathead engine it replaced. The Knucklehead's engine, with its advanced design and durability, became a cornerstone of Harley-Davidson's reputation for building powerful and reliable motorcycles.

The 1940-1947 Knucklehead models, covered by your service repair manual, represent a crucial period in the motorcycle's evolution. During World War II, Harley-Davidson, like other American manufacturers, shifted its focus to military production, resulting in a significant reduction in the production of civilian motorcycles. However, the Knucklehead continued to be produced, albeit in limited numbers, as a reliable and powerful machine for the US military. These models, with their distinctive styling and powerful performance, became iconic symbols of the American war effort. The post-war years saw a resurgence in motorcycle production, and the Knucklehead remained a popular choice for discerning riders, cementing its place in motorcycling history. Today, these vintage machines are highly sought-after by collectors and enthusiasts alike, regarded as a testament to Harley-Davidson's engineering prowess and enduring legacy.