🏷️ Basic Information Identification Make: Harley-Davidson Model: FL Knucklehead Codes Engine Code Variant: E (overhead valve, 61 cubic inch), F (overhead valve, 74 cubic inch) 👋 Introduction Market Position Positioning: Essential resource for owners and restorers of historically significant Harley-Davidson motorcycles. Competitive Analysis Comparison: Provides equivalent or superior detail to original factory service manuals, tailored for modern accessibility. Key Features Manual Features: Detailed sub-steps, critical notes/cautions/warnings, numbered instructions, bold figure numbers, detailed illustrations, enlarged insets, numbered table of contents, combined troubleshooting/electrical diagrams. 📋 Manual Details Coverage Areas Years Covered: 1940, 1941, 1942, 1943, 1944, 1945, 1946, 1947 Manual Type Type: Full Service Repair Manual Language Language: English Format Format: PDF 📖 Manual Coverage Systems Covered Engine: Detailed diagnosis, repair, overhaul, and tuning of Knucklehead OHV engines (E and F series). Transmission: Service and repair of the 4-speed constant mesh transmission, including clutch and primary drive. Electrical System: Comprehensive coverage of ignition, lighting, charging system, and wiring diagrams. Fuel System: Carburetor (Linkert M series) diagnosis, adjustment, and overhaul. Suspension And Steering: Front fork (often springer or hydraulic telescopic) and rear suspension servicing; steering head bearing adjustment. Brakes: Service and adjustment of drum brake systems. Frame And Bodywork: Frame inspection, component mounting, and body panel adjustments. Procedures Included Maintenance: Scheduled maintenance, lubrication, adjustments, and component checks. Troubleshooting: Systematic diagnostic procedures for common and uncommon faults. Repair: Step-by-step repair instructions for all major components and systems. Rebuilding Refurbishment: Detailed procedures for complete engine and transmission rebuilds. Technical Depth Depth: Comprehensive, suitable for professional technicians and experienced DIY mechanics aiming for full restoration. 📊 Manual Specifications File Format PDF Quality: High-resolution, fully printable with searchable text. Print Quality Printability: All pages are printable. Binding Type Binding: Digital Download (PDF) - No physical binding. Paper Type Paper Type: Not applicable (Digital Download). ⚙️ Engine Specifications Primary Engine Engine Type: Air-cooled, four-stroke, V-twin OHV (Knucklehead) Performance Engine Displacement E Series: 61 cubic inches (1000cc) Engine Displacement F Series: 74 cubic inches (1200cc) Fuel System Carburetor Type: Linkert M-series (e.g., M5, M74) Ignition System Ignition Type: Battery and coil ignition with timer, often a distributor-less system for earlier models. 🔧 Transmission Standard Transmission Type: 4-speed constant mesh Optional Optional Transmissions: Not applicable for this specific period/model. Features Clutch Type: Dry, multi-plate, foot-clutch operation with hand-lever actuation. 📐 Dimensions Exterior Wheelbase: Approximately 56.5 inches (varies slightly by model year and specific configuration). Weights Dry Weight: Approximately 475-530 lbs (depending on E or F series and specific options). 🛡️ Safety Features Ratings Safety Features Era: Brake performance and tire adhesion were primary safety considerations; minimal active safety features by modern standards. Active Features Active Safety: Drum brakes, mechanical indicators (trafficators) on some models. Passive Features Passive Safety: Robust frame construction, basic rider protection via motorcycle design. 💡 Technology Features Infotainment Infotainment Features: Not applicable. These are classic motorcycles focused on mechanical purity. Driver Assistance Driver Assistance Systems: Not applicable. Connectivity Connectivity Features: Not applicable. 🔧 Maintenance Service Intervals Oil Change Interval: Typically every 1000-2000 miles or annually, depending on usage and oil type. The manual will provide specific recommendations. Tune Up Interval: Recommended every 3000-5000 miles, including spark plug inspection, ignition timing adjustment, and carburetor tuning. Fluid Specifications Engine Oil Type: Typically SAE 50 or 60 weight oil, depending on ambient temperature. Manual will specify exact grades and API classifications. Transmission Oil Type: Gear oil, often SAE 90 or higher. Specific viscosity and GL rating will be detailed in the manual. Primary Chain Case Oil: Often a mix of primary lubricant and engine oil, or specialized primary fluid. Manual will confirm. Known Issues Common Wear Points: Valve guides, camshaft bushings, mainshaft and countershaft bearings in the transmission, and rocker box gaskets are common areas requiring attention. Carburetor Issues: Linkert carburetors can be prone to worn throttle shafts, needle wear, and fuel delivery inconsistencies, requiring careful tuning and rebuilds. Oil Leaks: Older Harleys are notorious for minor oil leaks from various seals and gaskets; maintaining proper seal integrity is crucial. 📚 Vehicle History Brand Heritage Brand Legacy: Harley-Davidson's legendary reputation for building powerful, reliable, and iconic American motorcycles. Model Evolution Knucklehead Evolution: The Knucklehead (introduced 1936) was a revolutionary design for Harley-Davidson, featuring distinctive rocker box covers resembling knuckles. It succeeded the Flathead and preceded the Panhead. Production Production Years: 1936-1947 Wartime Production: During World War II, Harley-Davidson produced many motorcycles for military use (e.g., WLA Liberator), with civilian production continuing for essential services and limited domestic sales. 🏆 Awards & Recognition Recognitions Historical Significance: Recognized as one of the most iconic and historically significant American motorcycles, a pinnacle of pre-Panhead Harley-Davidson engineering. Ratings Collectibility: Highly collectible and sought after by vintage motorcycle enthusiasts and collectors worldwide. Certifications Original Factory Certification: The manual is designed to replicate the detail and accuracy of original Harley-Davidson factory service documentation.