This manual covers Big Twin motorcycles, specifically the Knucklehead and Flathead models produced between 1940 and 1947. These iconic V-twins represent a significant period in the brand's history, with the Knucklehead introducing overhead valve technology and improved performance over the preceding Flathead designs. Engineered for reliability and a distinctive riding experience, these motorcycles are highly valued by collectors and enthusiasts for their robust construction and historical significance. The manual details engine codes such as E, F, FL, U, UL, and ULH, catering to the specific configurations of these classic machines.

This comprehensive service and repair manual provides detailed guidance for the maintenance and restoration of your Big Twin. It covers all essential systems, including engine lubrication and overhaul, carburetor servicing, electrical systems, drivetrain components, and chassis maintenance. You will find in-depth procedures for troubleshooting, routine maintenance, engine rebuilds, and tuning adjustments for ignition and carburetors. With 165 pages of high-resolution digital content, this manual is an indispensable resource for owners and technicians alike, ensuring the continued performance and authenticity of these legendary motorcycles.