Model:
Flathead (WL, WLA, UL, ULA, W, R, etc.)
Model Designations:
WL (Lightweight Solo), WLA (Lightweight Army), UL (1200cc Heavyweight Solo), ULA (1200cc Heavyweight Army), W (Civilian version of WL), R (older 750cc model family ancestor)
Engine Code Family:
Flathead (Side-valve V-twin)
Category:
Classic Motorcycle Service Manual
Target Audience:
Harley-Davidson Flathead owners, restorers, mechanics, and enthusiasts working on models from 1940-1947.
Value Proposition:
Provides essential, detailed technical information crucial for maintaining and repairing these iconic vintage motorcycles, bridging the gap left by unavailable original print manuals or offering a convenient digital format.
Availability:
Instant PDF download, eliminating shipping delays and costs.
Comprehensiveness:
Covers a wide range of mechanical and electrical systems specific to the Flathead era.
Engine:
Detailed inspection, disassembly, assembly, troubleshooting, and repair of the Flathead V-twin engine, including top-end (cylinders, heads, valves, lifters) and bottom-end (crankcase, crankshaft, connecting rods, bearings, oil pump).
Transmission:
Coverage for the hand-shifted, foot-clutched 4-speed constant mesh transmission, including disassembly, assembly, gear inspection, shifting mechanism, and clutch operation.
Fuel System:
Includes information on Stromberg, Linkert (e.g., M-series carburetors), fuel tank, fuel lines, and fuel petcock maintenance and adjustment.
Electrical System:
Covers ignition system (magneto, battery ignition systems depending on specific model/year variations), lighting circuits, generator/charging system, wiring diagrams, and troubleshooting for electrical faults.
Suspension:
Front fork (e.g., springer fork) overhaul, lubrication, and adjustment; rear suspension details (rigid frame often, but some models might have basic spring seat mounts).
Brakes:
Information on drum brake systems (front and rear), including brake shoe replacement, drum inspection, and brake rod adjustment.
Frame And Bodywork:
Includes details on frame inspection, mounting points, fenders, fuel tank mounting, seat mounting, and basic body panel alignment.
Wheels And Tires:
Information on wheel bearing maintenance, tire pressure recommendations, and spoke wheel truing (where applicable).
Routine Maintenance:
Oil changes, filter replacement, spark plug service, battery maintenance, chain adjustment, lubrication points.
Engine Rebuilding:
Comprehensive procedures for complete engine teardown, component inspection (wear limits), and reassembly with torque specifications.
Transmission Repair:
Detailed steps for transmission disassembly, clutch plate replacement, gear inspection, and reassembly.
Carburetor Overhaul:
Instructions for cleaning, rebuilding, and adjusting common carburetor models used on these bikes.
Electrical Troubleshooting:
Systematic approaches to diagnose and repair common electrical issues, including ignition timing and charging system faults.
Suspension Service:
Fork oil changes, seal replacement, and adjustments for optimal ride quality.
Brake Adjustment:
Proper adjustment of brake levers and rods for effective braking.
Wheel Alignment:
Spoke tensioning and truing procedures for maintaining wheel integrity.
Depth:
Comprehensive, covering everything from basic tune-ups and fluid changes to complete engine and transmission overhauls, including detailed specifications and troubleshooting guides.
Engine Type:
Air-cooled, 45-degree V-twin, side-valve (Flathead)
Displacement Variants:
Typically 45 cubic inches (737cc) for WL/WLA models, and 74 cubic inches (1200cc) for UL/ULA models. Some earlier 750cc (R model) information might be cross-referenced or implicitly covered.
Bore X Stroke 45Ci:
3.0625 in x 3.125 in (77.79 mm x 79.38 mm)
Bore X Stroke 74Ci:
3.4375 in x 4.00 in (87.31 mm x 101.6 mm)
Compression Ratio Typical:
Approximately 5.0:1 to 6.0:1 depending on year and specific model.
Horsepower 45Ci Approx:
Around 20-24 HP at 4800 RPM.
Torque 45Ci Approx:
Around 30-35 lb-ft at 3000 RPM.
Horsepower 74Ci Approx:
Around 30-35 HP at 4500 RPM.
Torque 74Ci Approx:
Around 45-50 lb-ft at 3000 RPM.
Carburetor Types:
Primarily Linkert (e.g., M, M-series) and sometimes Stromberg models. Specific jetting and settings are crucial and detailed in the manual.
Fuel Type:
Leaded gasoline (historically). Modern ethanol-free or low-ethanol gasoline with appropriate octane is recommended, and lead substitutes may be advised.
Type:
Total loss (pre-mix or drip oiler) or recirculating oil systems depending on model and year. The manual will clarify specific systems.
Oil Type Recommendation:
Historically, specific Harley-Davidson branded oils or SAE 50/60 weight oils. Modern recommendations often suggest specific motorcycle-specific oils (e.g., V-twin specific) with appropriate viscosity and additive packages.
Oil Change:
Typically every 1,000-1,500 miles, or as specified in the manual for specific lubrication systems. Recirculating systems may have different intervals.
Spark Plug Service:
Check and clean/gap spark plugs every few thousand miles, replace as needed. Manual will specify correct plug types (e.g., Champion H-10, H-12).
Valve Adjustment:
Periodic valve lash adjustment recommended, usually every 3,000-5,000 miles. Manual provides exact clearances.
Engine Oil:
SAE 50 or SAE 60 motorcycle-specific oil. Check manual for exact viscosity and type based on operating temperature. (e.g., Harley-Davidson 10W-30 for some later variations, but 50/60 is common for this era).
Transmission Oil:
SAE 60 gear oil or Harley-Davidson transmission oil.
Primary Chain Case Oil:
Often the same as transmission oil or a specific primary lubricant. Manual will detail.
Fork Oil:
Specific grade of suspension oil, typically SAE 10W or 20W. Manual will specify type and quantity.
Oil Leaks:
Common due to aging seals, gaskets, and primitive sealing designs. Manual provides procedures for addressing leaks.
Carburetor Adjustment:
Linkert carburetors can be finicky; require precise adjustment for optimal performance and starting. Manual guides tuning.
Ignition Timing:
Proper ignition timing is critical for performance and engine health. Manual details timing procedures, often using timing marks.
Generator Charging:
Generator output can degrade over time, requiring servicing or replacement. Manual covers testing and troubleshooting.
Clutch Slippage:
Can occur with worn clutch plates or improper adjustment. Manual covers replacement and adjustment.
Foundation:
Harley-Davidson Motor Company founded in 1903, a cornerstone of American motorcycling.
Flathead Development:
The 'Flathead' engine, with its side-valve configuration, was first introduced in the 1920s and became a workhorse for Harley-Davidson, evolving through various displacements (45ci, 74ci, 80ci) and models. The 1940-1947 period represents a mature stage of this engine's development, heavily influenced by military contracts (WLA).
Military Influence:
The WLA (45ci) model was produced in large numbers for military use during World War II, significantly shaping Harley-Davidson's production and development during this period. Many civilian models benefited from the robust engineering and standardization driven by military demand.
Manufacturing Location:
Milwaukee, Wisconsin, USA.
Wartime Production:
Production shifted heavily towards military contracts (WLA) during WWII, with civilian production significantly reduced or halted.
