Model Years Covered:
1940, 1941, 1942, 1943, 1944, 1945, 1946, 1947
Manual Product Code:
Harley Big Twins 1940-1947 Service Repair Manual PDF
Target Audience:
Restorers, collectors, and mechanics specializing in vintage Harley-Davidson motorcycles.
Value Proposition:
Provides essential technical data for maintaining and repairing historically significant Harley-Davidson Big Twins.
Alternatives:
Original factory service manuals (rare and expensive), other aftermarket manuals (may vary in completeness).
Historical Significance:
Covers a pivotal era in Harley-Davidson's Big Twin development, including the transition to OHV designs.
Comprehensive Coverage:
Addresses the full spectrum of maintenance, repair, and troubleshooting needs for these models.
Digital Format:
Convenient PDF format allows for easy searching and access on various devices.
Primary Coverage:
Comprehensive service and repair for Harley-Davidson Big Twin motorcycles.
Engine Systems:
Engine assembly, disassembly, tuning, lubrication, cooling, fuel system, ignition system.
Transmission Drivetrain:
Gearbox service, clutch operation, drive chain maintenance.
Chassis Suspension:
Frame, forks, shocks, wheels, tires, bearings.
Electrical Systems:
Wiring diagrams, lighting, ignition coils, battery, generator/alternator (depending on model year).
Brakes:
Brake system maintenance and repair (drum brakes typical for this era).
Bodywork Fittings:
Fenders, fuel tank, seat, handlebars, controls.
Troubleshooting:
Diagnostic procedures for common problems and performance issues.
Estimated Page Count:
High (typical for comprehensive service manuals, likely 300+ pages).
Type:
Service Repair Manual
Engine Types:
Flathead V-twin engines (e.g., 61 cubic inch OHV 'Knucklehead' and potentially early OHV 'Panhead' introductions towards the end of this period).
Carburetion:
Detailed information on Schebler, Linkert, or other contemporary carburetors used.
Ignition:
Battery-generator ignition systems, timing adjustments, points and condenser service.
Lubrication System:
Wet-sump or dry-sump oiling systems, oil pump servicing, oil filter replacement (if applicable).
Clutch Transmission:
Hand-clutch, foot-shift operation, transmission gear inspection and replacement.
Suspension Forks:
Girder forks, springer forks, hydraulic damping systems (if present).
Electrical Components:
Headlight, taillight, horn, battery charging system, voltage regulation.
Routine Maintenance:
Oil changes, spark plug replacement, chain adjustment, brake checks, lubrication points.
Engine Rebuild:
Piston and ring replacement, cylinder honing, valve lapping and seating, crankshaft service.
Transmission Overhaul:
Gearbox disassembly, bearing replacement, shift mechanism repair.
Electrical Troubleshooting:
Locating shorts, open circuits, diagnosing charging system issues using wiring diagrams.
Carburetor Adjustment:
Idle speed, fuel mixture adjustments, float level setting.
Ignition Timing:
Setting ignition timing using static or dynamic methods.
Wheel Hub Service:
Wheel bearing replacement, spoke tension adjustment (for wire wheels).
Depth:
Detailed, in-depth coverage suitable for professional mechanics and experienced DIY enthusiasts.
Diagnostics:
Advanced diagnostic procedures, symptom-based troubleshooting guides.
Specifications:
Includes critical torque values, clearances, and dimensional specifications.
Diagrams Illustrations:
Likely includes exploded views, wiring diagrams, and step-by-step procedural illustrations.
Engine Configuration:
Air-cooled, 45-degree V-twin
Displacement Variants:
Primarily 74 cubic inches (1200cc) OHV for Big Twins; some earlier or specific models might have 61 cubic inches (1000cc) OHV.
Engine Family:
Knucklehead (40-47, with Panhead introduction likely in 48, but overlap in technology/knowledge is relevant)
Horsepower Approximate:
Varies by year and specific engine, but typically in the 20-30 HP range for this era.
Torque Approximate:
Varies by year and specific engine, emphasizing low-end grunt.
Carburetor Types:
Schebler, Linkert, or similar vintage carburetors.
Fuel Type:
Leaded gasoline (typically 87-92 octane).
Fuel Delivery:
Gravity feed from fuel tank to carburetor.
Type:
3-speed or 4-speed constant mesh, hand-clutch, foot-shift (left-hand controls).
Variants:
While less common for Big Twins of this era, some specialized models or modifications might exist.
Clutch Type:
Dry multi-plate clutch, operated by hand lever.
Shift Mechanism:
Foot-operated shift lever controlling engagement of gears.
Wheelbase Approximate:
Typically around 58-60 inches, depending on the specific model.
Seat Height Approximate:
Varies, but generally lower than modern bikes.
Cargo Capacity:
None standard; optional saddlebags or luggage racks.
Dry Weight Approximate:
Generally in the range of 500-600 lbs.
Safety Standards:
No formal crash ratings like modern vehicles; emphasis on rider skill and mechanical condition.
Braking System:
Drum brakes front and rear. Effective for the era but require more input than modern disc brakes.
Lighting:
Headlight, taillight, and stoplight. Electrical system reliability is key.
Frame Construction:
Steel frame, robust for its time.
Oil Change Interval:
Typically every 1000-2000 miles, or as recommended in the manual.
Tune Up Interval:
Periodic tune-ups including ignition timing, carburetor adjustment, and valve lash checks.
Chain Adjustment:
Regularly check and adjust drive chain tension.
Engine Oil Type:
API SG or HD-spec straight-weight mineral oil (e.g., SAE 50 or SAE 60, depending on ambient temperature).
Engine Oil Capacity:
Refer to manual, typically around 4-5 quarts.
Transmission Oil Type:
Motorcycle-specific gear oil (e.g., SAE 80 or 90).
Primary Chain Case Oil:
Often shared with transmission, or specific oil depending on setup.
Oil Leaks:
Common due to aging seals and gaskets. Requires regular inspection and potential replacement.
Carburetor Clogging:
Due to old fuel deposits, requires periodic cleaning and rebuilding.
Ignition Timing Drift:
Points and condenser can wear, affecting timing and performance.
Wear And Tear:
General wear on engine internals, bearings, and suspension components due to age.
Founding:
Harley-Davidson Motor Company founded in 1903.
Legacy:
Iconic American motorcycle manufacturer known for V-twin engines and robust build.
Predecessors:
Evolutions of earlier Big Twin designs, including the 'Flathead' models.
Period Significance:
These models represent a transitionary period, moving towards more overhead valve designs that would define future Big Twins.
Manufacturing Location:
Milwaukee, Wisconsin, USA
Production Period:
1940-1947, with specific models varying slightly within this range.
