Model:
Flathead (E, EL, F, FL, G, GE, U, UL, UH, UA, VL, VLD, VLH, W, WL, WLA, WLDA)
Model Variant:
V-Twin OHV
Years Covered:
1940, 1941, 1942, 1943, 1944, 1945, 1946, 1947
Engine Codes:
E, EL, F, FL, G, GE, U, UL, UH, UA, VL, VLD, VLH, W, WL, WLA, WLDA
Significance:
Essential resource for owners and restorers of iconic Harley-Davidson Flathead motorcycles from a pivotal era in American motorcycling.
Value Proposition:
Provides factory-correct procedures and specifications, crucial for accurate maintenance, repair, and restoration, which third-party manuals may lack.
Coverage Scope:
Unparalleled depth for the specific model years and engine configurations it covers, reflecting the original factory documentation.
Authenticity:
Represents the official and most authoritative information available for these vintage machines.
Audience:
Harley-Davidson enthusiasts, vintage motorcycle restorers, mechanics specializing in classic American motorcycles.
Primary Coverage:
Complete Service, Repair, and Workshop
Secondary Coverage:
Troubleshooting, Maintenance, Overhaul, Specifications
Estimated Page Count:
Likely 500-800+ pages (typical for comprehensive factory manuals of this era, exact count varies)
Type:
Factory Service Manual / Workshop Manual
Engine:
Flathead V-Twin, lubrication system, cooling (air), fuel system (carburetion, fuel lines), ignition system (magneto/battery), valve train, cylinders, pistons, crankshaft, connecting rods, timing gears
Transmission:
3-speed, gearbox overhaul, clutch, primary drive, gear lubrication
Drivetrain:
Final drive, chain lubrication and adjustment, rear wheel hub
Chassis Frame:
Frame inspection, welding, steering head bearings
Suspension:
Front forks (leaf spring/hydraulically damped), rear suspension (rigid or sprung seat post), shock absorber servicing (if applicable to specific models)
Brakes:
Front and rear brake system (drum brakes), brake shoe replacement, brake linkage adjustment, hydraulic fluid (if applicable, though primarily mechanical for this era)
Electrical System:
Battery charging system (generator/alternator, rectifier), ignition timing, lighting (headlight, taillight, signals), wiring diagrams, starter system (if equipped), horn
Bodywork Fittings:
Fenders, fuel tank, seat, handlebars, control cables, exhaust system, stands
Maintenance:
Scheduled servicing, oil changes, filter replacement, lubrication points, ignition timing adjustment, carburetor tuning, brake adjustments, chain maintenance
Repair:
Engine overhaul (top-end and bottom-end), transmission rebuild, clutch replacement, fork seal replacement, brake system repair, electrical component troubleshooting and repair, carburetor rebuilding
Troubleshooting:
Diagnostic procedures for common running issues, electrical faults, ignition problems, fuel delivery issues, mechanical noise identification
Specifications:
Detailed torque specifications, clearance measurements, timing marks, fluid capacities, electrical resistance values
Rebuilding:
Complete engine rebuild, gearbox rebuild, carburetor rebuild with part identification
Depth:
Comprehensive, covering all aspects from basic maintenance to full engine and transmission overhauls. Designed for qualified mechanics and experienced enthusiasts.
Engine Type:
Overhead Valve (OHV) V-Twin
Engine Displacement Cu In:
74 cubic inches (1212cc) for Big Twin (U, UL, UH, UA, F, FL); 45 cubic inches (737cc) for Medium Twin (E, EL, G, GE, W, WL, WLA)
Bore Stroke 74 Ci:
3-7/16" x 4-1/4" (approximate, specific models may vary slightly)
Bore Stroke 45 Ci:
2-3/4" x 4" (approximate, specific models may vary slightly)
Horsepower 74 Ci:
Approx. 20-30 HP (varies by specific model and tuning)
Horsepower 45 Ci:
Approx. 18-25 HP (varies by specific model and tuning)
Torque Specs:
Refer to specific model sections within the manual for torque values.
Carburetor Models:
Linkert M-series (e.g., M51, M53, M74B, M74A)
Fuel Type:
Gasoline (with appropriate octane rating for the era, typically lower than modern fuels)
System Type:
Total Loss (oil is consumed with fuel/exhaust, requires frequent replenishment)
Type:
Battery and Coil or Magneto Ignition (depending on model and year)
Type:
3-speed constant mesh, foot-shifted, hand-clutched
Optional Features:
N/A for this period; 3-speed was standard across most models.
Clutch Type:
Dry multi-plate, operated by hand lever on left handlebar
Primary Drive:
Roller chain to transmission
Gearbox Oil Spec:
Refer to manual for specific viscosity, typically SAE 50 or SAE 60 motor oil
Safety Standards:
N/A (Pre-dates modern standardized safety ratings like NHTSA or IIHS)
Braking System:
Mechanical drum brakes front and rear. Effectiveness varies by model and condition.
Lighting:
Headlight, taillight, and possibly brake light (depending on year/model). Generator output is critical for reliable lighting.
Frame Design:
Robust steel frame, but lacks modern crumple zones or passenger safety restraints.
Oil Change Interval:
Every 500-1000 miles (or as specified in the manual), due to total-loss lubrication system.
Tune Up Interval:
As needed, but typically recommended every 2000-3000 miles for ignition timing, carburetor adjustment, and general inspection.
Engine Oil Type:
Refer to manual; typically SAE 50 or SAE 60 mineral oil. Special attention to viscosity in varying temperatures.
Transmission Oil Type:
Refer to manual; typically SAE 50 or SAE 60 mineral oil.
Primary Chain Case Oil:
Refer to manual; typically SAE 50 or SAE 60 mineral oil.
Engine Oil Capacity:
Approx. 3-4 quarts (total system including oil tank)
Transmission Oil Capacity:
Approx. 1 pint (refer to manual for exact fill level)
Oil Leaks:
Common due to age, worn seals, gaskets, and breather systems. Proper diagnosis and repair are key.
Carburetor Tuning:
Linkert carburetors can be finicky and require regular adjustment (idle speed, air/fuel mixture) for optimal performance. Jetting and float levels are critical.
Ignition Timing:
Crucial for proper running; requires precise adjustment using timing marks or specialized equipment.
Valve Adjustment:
Requires periodic adjustment to maintain proper clearances for valve seating and operation.
Generator Output:
Can be a source of electrical issues if not functioning correctly, affecting battery charging and lighting.
Oil Filter Part Number:
N/A (These models typically used oil strainers or screens, not modern spin-on filters. The manual will detail cleaning procedures for these.)
Spark Plug Spec:
Refer to manual; typically Champion H10 or equivalent for the era.
Heritage Context:
Harley-Davidson, established in 1903, is one of the longest-standing motorcycle manufacturers in the world. The Flathead engine family represents a cornerstone of their pre-war and World War II era output.
Flathead Development:
The Flathead engine was introduced in 1929 and evolved through various displacements (45ci, 51ci, 74ci, 80ci) and configurations (side-valve) for civilian and military use. The 1940-1947 period covers significant developments and widespread use, including the WLA model for military service.
Production Locations:
Milwaukee, Wisconsin, USA
Military Variants:
The WLA (45 cubic inch) model was produced in significant numbers for the US Army and its allies during World War II, making it one of the most recognizable Harley-Davidsons.
Historical Impact:
The Flathead models, particularly the WLA, played a significant role in military logistics during WWII, earning them a place in historical significance. Civilian models are highly sought after by collectors and enthusiasts.
Collector Value:
High collector demand and appreciation for their historical importance, engineering simplicity, and iconic styling.
Manual Authenticity:
Represents official factory documentation, highly valued for accuracy in restoration and repair.
