Market Segment:
Classic American V-Twin Motorcycle
Competitive Landscape 1978:
Competed with other large-displacement V-twins from American manufacturers and emerging Japanese models. Differentiated by its iconic styling, V-twin rumble, and customization potential.
Distinctive Attributes 1978 Flh:
Shovelhead engine, classic 'Batwing' fairing (on FLH models), comfortable touring ergonomics, robust chassis for its era, emphasis on rider experience and customization.
Primary Coverage:
Service, Repair, Maintenance, Troubleshooting, Electrical Schematics, Specifications
Diagnostic Procedures:
Includes procedures for diagnosing common mechanical and electrical problems, often using a systematic approach.
Estimated Page Count:
300+
Manual Type:
Factory Service Repair Manual
Manual Origin:
Official Factory Service Manual, providing authorized repair information directly from the manufacturer.
Engine Systems:
Engine disassembly, assembly, tuning, carburetor service (e.g., Keihin Butterfly), ignition system (points and timing), oil pump, lubrication, cooling system (air-cooled)
Transmission Systems:
Four-speed constant mesh transmission service, clutch operation and adjustment, primary drive maintenance
Electrical Systems:
Wiring diagrams, charging system (generator/alternator), lighting, ignition coil, starter motor, battery service, troubleshooting electrical faults
Chassis Systems:
Frame inspection, front suspension (forks), rear suspension (shocks), wheel bearings, steering head bearings, braking system (drum brakes), exhaust system
Bodywork And Trim:
Fenders, fuel tank, seat, handlebars, controls, fairings (if applicable)
Fuel System Details:
Carburetor rebuilding, fuel tank servicing, fuel line replacement, fuel petcock operation.
Maintenance Procedures:
Routine servicing, oil changes, filter replacements, chain adjustment, spark plug replacement, brake adjustments, battery care
Repair Procedures:
Engine rebuilds, transmission overhauls, suspension component replacement, electrical system diagnostics and repair, brake system overhaul
Troubleshooting Guides:
Step-by-step diagnostic procedures for common and uncommon issues, fault code interpretation (if applicable to the era), symptom-based troubleshooting
Specification Tables:
Torque specifications, clearances, fluid capacities, electrical resistance values, timing settings
Special Tool Requirements:
Details any specialized tools required for specific repairs or adjustments (e.g., primary chain alignment tools, ignition timing tools).
Depth Of Coverage:
Comprehensive; covers everything from basic adjustments to complete engine and transmission rebuilds. Includes detailed exploded diagrams and component identification.
Wiring Schematics Detail:
Detailed, often color-coded, electrical diagrams illustrating the complete wiring harness and component connections for accurate troubleshooting.
File Format:
PDF (Portable Document Format)
Searchability:
PDF format generally allows for text searching if the PDF was created from a digital source or has been OCR'd.
Print Quality:
High-resolution, suitable for printing individual pages or the entire manual. Text is generally searchable if OCR processed.
Binding Type When Printed:
Spiral-bound or three-hole punched for binder (user-dependent)
Paper Type When Printed:
Standard printer paper (user-dependent)
Engine Type:
Air-cooled, 45-degree V-twin
Displacement:
73.7 cu in (1207 cc)
Bore X Stroke:
3.4375 in x 4.00 in (87.31 mm x 101.6 mm)
Compression Ratio:
8.0:1 (typical)
Valvetrain:
Overhead valve (OHV), pushrod actuated
Cylinder Heads:
Cast aluminum (typically aluminum alloy for 1978 models)
Carburetor Jetting Recommendations:
Manual provides base jetting specifications, with guidance on adjustments for altitude and atmospheric conditions.
Horsepower Estimated:
60-70 HP (at crankshaft, estimated)
Torque Estimated:
75-85 lb-ft (at crankshaft, estimated)
Carburetor:
Keihin Butterfly (e.g., 34mm or 38mm, model dependent)
Fuel Type:
Unleaded gasoline (lead substitute may be recommended for older engines or specific components if hardened valve seats are not present)
Ignition Type:
Battery and Coil with Spark Advance (Points Ignition)
Oil Capacity:
Approximately 3 US quarts (2.8 Liters) for the dry-sump system
Wheelbase:
Approximately 63.2 inches (1605 mm)
Length:
Approximately 91.5 inches (2324 mm)
Height:
Approximately 50.5 inches (1283 mm) to top of fairing
Dry Weight:
Approximately 620-660 lbs (281-299 kg), depending on configuration
Gross Vehicle Weight Rating Gvwr:
Not typically specified with a GVWR in the same way as cars, but laden weight should be considered for safe operation.
Safety Ratings:
Motorcycles of this era were not subjected to standardized crash testing or safety ratings like modern automobiles. Safety was primarily dependent on rider skill and basic mechanical integrity.
Active Safety Features:
Drum brakes (front and rear), handlebar controls for braking and throttle, stable chassis design for its time.
Passive Safety Features:
No active electronic safety aids (ABS, traction control). Rider protection relies heavily on protective gear.
Infotainment System:
N/A - Motorcycles of this era did not feature electronic infotainment systems as understood today. Focus was on basic instrumentation (speedometer, tachometer, oil pressure, neutral indicator).
Driver Assistance Features:
N/A - No electronic driver assistance features were available on motorcycles in 1978.
Connectivity Features:
N/A - No integrated connectivity features.
Oil Change Interval:
Typically every 2,000-3,000 miles or annually, whichever comes first (refer to manual for precise recommendation).
Primary Chain Tensioner Adjustment:
Check and adjust every 2,000-3,000 miles.
Spark Plug Replacement:
Recommended every 5,000-10,000 miles, or as needed based on condition.
Tune-Up Frequency:
Annual tune-ups recommended, including ignition timing checks, carburetor adjustments, and valve lash checks.
Engine Oil Type:
Viscosity typically SAE 20W-50 or SAE 50 for air-cooled V-twins. Specific Harley-Davidson recommended oils or equivalent motorcycle-specific oils are advised.
Transmission Oil Type:
Gear oil, typically SAE 80W-90 or Harley-Davidson's own transmission lubricant.
Primary Drive Fluid Type:
Harley-Davidson Primary Chaincase Lubricant (or equivalent).
Brake Fluid Type:
DOT 3 or DOT 4 brake fluid (check manual for specific recommendation and compatibility).
Common Shovelhead Issues:
Oil leaks (especially from rocker boxes and primary cover), valve seat wear, starter solenoid issues, primary chain wear, carburetor tuning sensitivity, potential for oil dilution in the primary.
1978 Specific Considerations:
Early models may have had cast iron heads and cylinders which could be prone to cracking under severe heat. Later models (like 1978) were more refined but still require diligent maintenance.
Harley Davidson Legacy:
Founded in 1903, Harley-Davidson is the oldest American motorcycle manufacturer in continuous operation, synonymous with American motorcycling culture, V-twin engines, and customization.
Shovelhead Development:
The Shovelhead engine, introduced in 1966, succeeded the Panhead. It was characterized by its distinctive rocker box covers resembling shovels. The FLH represented the touring variant of the Big Twin platform.
Shovelhead Production Years:
1966-1984
1978 Model Year Context:
The 1978 model year falls into the later part of the Shovelhead era, featuring evolutionary improvements over earlier versions. This was a period where Harley-Davidson was navigating challenges and laying groundwork for future models.
