Model Variants:
Various including EL, FL, UL, WL models
Engine Code Prefix:
E (1000cc OHV), F (1200cc OHV), U (1200cc SV), W (750cc SV)
Historical Context:
The Harley-Davidson Flathead engine was a workhorse for the brand, powering a wide range of civilian and military motorcycles during a transformative period in American history. This manual is essential for owners and restorers of these iconic machines.
Comparison:
During its production, Harley-Davidson dominated the American motorcycle market. This manual provides the factory-level detail necessary to maintain and repair these robust machines, distinguishing them from contemporary offerings.
Manual Value:
Provides essential information for proper maintenance, repair, and restoration of Harley-Davidson Flathead motorcycles from 1940-1947, ensuring authenticity and operational reliability.
Years Covered:
1940, 1941, 1942, 1943, 1944, 1945, 1946, 1947
Estimated Pages:
300-500 (typical for comprehensive service manuals of this era, exact count depends on publisher)
Type:
Service and Repair Manual
Engine:
Complete overhaul, disassembly, assembly, tuning, troubleshooting of Flathead V-twin engines (OHV and SV variants)
Transmission:
Disassembly, assembly, repair, and adjustment of 4-speed constant mesh transmissions
Clutch:
Service and repair of dry clutch assemblies
Fuel System:
Carburetor overhaul (e.g., Linkert), fuel tank, fuel lines, fuel pump (if applicable)
Electrical System:
Ignition system (magneto/distributor), lighting, charging system (generator), wiring diagrams, starter motor
Brakes:
Service and adjustment of drum brakes (front and rear)
Suspension:
Front fork (spring fork, girder fork) overhaul and adjustment, rear suspension (if applicable, e.g., plunger suspension)
Frame And Bodywork:
Frame inspection, body panel alignment, fenders, fuel tank mounting
Wheels And Tires:
Wheel bearing service, spoke tensioning, tire changes, wheel balancing
Maintenance:
Regular servicing, lubrication, cleaning, component checks, adjustments
Troubleshooting:
Diagnostic flowcharts, common problems and solutions for all major systems
Repair:
Detailed step-by-step repair instructions for all components and systems
Rebuilds:
Complete engine and transmission rebuild procedures
Diagnostics:
Ignition timing, carburetor tuning, compression testing
Depth:
Comprehensive, covering all aspects from basic maintenance to complete engine rebuilds and advanced troubleshooting.
Engine Family:
Flathead V-twin
Available Displacements:
750cc (45 ci), 1000cc (61 ci), 1200cc (74 ci)
Valve Configuration:
Overhead Valve (OHV) for E/F/FL/EL series, Side Valve (SV) for U/UL/W/WL series
Bore Stroke El:
3.0625" x 3.375" (77.8 mm x 85.7 mm)
Bore Stroke Fl:
3.4375" x 3.96875" (87.3 mm x 100.8 mm)
Bore Stroke Ul:
3.4375" x 4.125" (87.3 mm x 104.8 mm)
Bore Stroke Wl:
2.9375" x 4.0625" (74.6 mm x 103.2 mm)
Horsepower El:
Approx. 24-28 HP (varies by tune and year)
Horsepower Fl:
Approx. 30-34 HP (varies by tune and year)
Torque Fl:
Approx. 45-50 ft-lbs (varies by tune and year)
Carburetor Type:
Linkert M-series (e.g., M51, M74, M75)
Fuel Type:
Gasoline (typically lower octane than modern fuels, leaded was common)
Ignition System:
Battery ignition with distributor (later models) or magneto ignition (earlier/military)
Safety Standards:
N/A (Motorcycles of this era were not subjected to modern crash test ratings. Safety emphasis was on rider skill and machine reliability.)
Braking System:
Mechanical drum brakes, single-sided front and rear. Effective but require significant rider input and anticipation.
Frame Construction:
Robust steel frame designed for stability and load-carrying capacity.
Oil Change:
Every 1000-1500 miles or annually, whichever comes first. (Refer to manual for precise intervals and oil types).
Transmission Service:
Inspect and change transmission oil every 3000-5000 miles.
Ignition Timing:
Check and adjust as needed, especially after engine work or if performance is degraded. Intervals depend on usage and system condition.
Engine Oil Capacity:
Approx. 3 quarts (2.8 liters) for 74ci and 61ci engines.
Engine Oil Viscosity:
SAE 50 or SAE 60 recommended, depending on ambient temperature. (Consult manual for specific recommendations).
Transmission Oil Type:
Harley-Davidson Transmission Oil or equivalent SAE 50/60 (check manual for specific HD part numbers or grades).
Primary Chain Case Oil:
Typically a lighter oil or the same as the transmission oil, depending on the model year and configuration.
Oil Leaks:
Common due to aging seals, gaskets, and primitive crankcase ventilation. Manual provides procedures for addressing these.
Carburetor Idling:
Linkert carburetors can be finicky; requires proper tuning and cleaning. Manual details adjustments.
Ignition Timing Drift:
Can occur with wear in the distributor or magneto components. Manual covers timing procedures.
Rear Cylinder Overheating:
Can be an issue on older models with less efficient cooling; proper tuning and oil flow are critical. Manual addresses engine cooling.
Founding Era:
Harley-Davidson, founded in 1903, has a long and storied history in motorcycle manufacturing.
Flathead Introduction:
The Flathead engine series debuted in the 1920s and evolved significantly, becoming the backbone of Harley-Davidson's lineup through the 1930s and 1940s, including during WWII for military applications.
1940-1947 Context:
This period saw the Flathead as the primary engine for the majority of Harley-Davidson's civilian models (EL, FL, UL) and a crucial part of the war effort with the WLA and WLC models. Significant updates included improved lubrication, stronger frames, and telescopic forks.
Manufacturing Location:
Milwaukee, Wisconsin, USA
Wartime Production:
During World War II, Harley-Davidson's production shifted heavily towards military contracts, producing thousands of WLA (45 ci) and WLC (Canadian variant) models.
