🏷️ Basic Information

Make:

Harley-Davidson

Model:

Duo Glide

Year:

1964

Model Generation:

Second Generation (FL Series)

👋 Introduction

Historical Significance:

The 1964 Duo Glide represents a significant evolution in Harley-Davidson's FL line, featuring the iconic Duo-Glide suspension system, and serving as a bridge between the Panhead and the Shovelhead era. This manual is essential for preserving these classic motorcycles.

Manual Value Proposition:

This factory service manual provides the most accurate and complete information for maintaining and repairing the 1964 Duo Glide, offering a crucial advantage over generic aftermarket guides in accuracy and detail.

Diagnostic Focus:

Emphasizes systematic diagnostic procedures, enabling users to pinpoint issues efficiently rather than relying on guesswork.

Technical Accuracy:

Delivers manufacturer-verified technical data, torque specifications, tolerances, and OEM procedures.

📋 Manual Details

Primary Coverage:

Factory Service and Repair

Intended Audience:

Mechanics and DIY enthusiasts

Estimated Pages:

Refer to specific product listing for exact page count. Typical factory service manuals of this era range from 300-600 pages.

Type:

Factory Service Repair Manual

Language:

English

Format:

Print (Paperback or Hardcover)

📖 Manual Coverage

Engine:

Complete disassembly, assembly, inspection, and repair of the OHV V-twin engine (e.g., Panhead or early Shovelhead engine variants applicable to 1964 models).

Transmission:

Disassembly, assembly, adjustment, and repair of the 4-speed constant mesh transmission.

Clutch:

Service and adjustment of the clutch assembly.

Primary Drive:

Inspection and adjustment of the primary chain drive system.

Frame And Suspension:

Front fork (hydra-glide/duo-glide) disassembly, repair, and adjustment. Rear suspension servicing. Frame inspection and repair procedures.

Brakes:

Front and rear brake system inspection, adjustment, and repair (likely drum brakes for this era).

Electrical System:

Wiring diagrams, ignition system troubleshooting and repair (magneto or battery/coil), lighting system, starter system, generator/alternator (if applicable).

Fuel System:

Carburetor (e.g., Linkert) disassembly, cleaning, adjustment, and repair. Fuel tank and fuel line servicing.

Bodywork And Trim:

Fender removal and installation, seat servicing, fuel tank removal and installation, handlebar servicing.

Routine Maintenance:

Oil changes, lubrication points and schedules, filter replacement, spark plug checks and replacement.

Tune Up Procedures:

Ignition timing, carburetor adjustment, valve clearance adjustment.

Troubleshooting Guides:

Systematic diagnostic procedures for common and uncommon issues.

Component Rebuilds:

Detailed step-by-step instructions for complete engine, transmission, and carburetor rebuilds.

Installation And Removal:

Procedures for removing and installing major components and sub-assemblies.

Adjustment Procedures:

Precise instructions for adjusting clutch, brakes, ignition timing, and other critical systems.

Depth Of Coverage:

Comprehensive. Covers everything from basic maintenance and adjustments to complete engine and transmission rebuilds, including detailed specifications and tolerances.

📊 Manual Specifications

Digital Format Notes:

If sold as digital, typically PDF. Ensure clarity on searchability and image quality.

Print Quality:

Typically high quality, designed for workshop use. Includes clear diagrams and photographs.

Binding:

Often spiral-bound or sewn/glued binding for lay-flat use in a workshop environment.

Paper Quality:

Durable paper stock designed to withstand workshop conditions. May include coated pages for resistance to oil and grease.

⚙️ Engine Specifications

Engine Type:

Air-cooled, OHV (Overhead Valve), V-twin

Engine Designation:

Typically the Panhead engine (Evo Panhead) or very early Shovelhead designation may appear for 1964 models, check specific VIN range for exact engine.

Displacement:

Primarily 74 cubic inches (1200cc). Some models may have 80 cubic inches (1310cc) variants.

Horsepower Estimate:

Approx. 50-55 HP (varies by specific engine configuration and tuning).

Torque Estimate:

Approx. 65-70 ft-lbs (varies).

Carburetor:

Typically Linkert M-series carburetor (e.g., M74B, M74A).

Fuel Type:

Unleaded gasoline (higher octane recommended for vintage engines).

Ignition Type:

Battery and coil ignition system or Magneto ignition system depending on specific model variant.

Oil Type:

ZDDP-rich motorcycle-specific oil (e.g., SAE 50 or 20W-50 vintage motorcycle oil).

Oil Capacity:

Approx. 4 quarts (3.8 liters) for engine oil, plus transmission and primary chain case oil.

🔧 Transmission

Transmission Type:

4-speed, constant mesh, manual foot shift with heel-and-toe clutch lever.

Transmission Options:

N/A - Standard 4-speed transmission was the norm for this model.

Clutch Type:

Dry, multi-plate clutch.

Transmission Oil Type:

Harley-Davidson 4-speed transmission oil or equivalent.

📐 Dimensions

Wheelbase:

Refer to specific model documentation for precise wheelbase. Typically around 60-63 inches.

Length:

Refer to specific model documentation. Typically around 90-95 inches.

Dry Weight:

Approximately 500-550 lbs (227-250 kg) depending on trim and accessories.

Gross Vehicle Weight Rating:

Not typically specified in the same manner as cars, but refers to safe operating weight.

🛡️ Safety Features

Safety Ratings:

Motorcycles of this era were not subjected to modern crash testing or rating systems.

Braking System:

Drum brakes front and rear.

Lighting:

Headlight, taillight, brake light, turn signals (if equipped).

Frame Construction:

Steel tube frame.

Suspension Design:

Duo-Glide hydraulic suspension front and rear, offering improved ride comfort over previous models.

💡 Technology Features

Infotainment Systems:

N/A - Focus is on core mechanical and electrical systems. No modern infotainment.

Driver Assistance Features:

N/A - No electronic driver assistance features.

Connectivity Features:

N/A - No electronic connectivity features.

🔧 Maintenance

Oil Change Interval:

Typically every 1,000 to 2,000 miles (1600 to 3200 km) or annually, depending on usage.

Engine Tune Up Interval:

Recommended every 3,000 to 5,000 miles (4800 to 8000 km) or annually.

Transmission Service:

Transmission oil change recommended every 5,000 to 10,000 miles (8000 to 16000 km).

Engine Oil Viscosity:

SAE 50 or SAE 20W-50 motorcycle specific oil with adequate ZDDP content.

Transmission Oil Specification:

Harley-Davidson 4-speed transmission oil or equivalent.

Primary Chain Case Oil:

Typically SAE 50 or SAE 20W-50 motorcycle specific oil.

Carburetor Issues:

Linkert carburetors can be prone to wear and require meticulous cleaning and adjustment for proper operation.

Oil Leaks:

Common across vintage motorcycles due to aging seals and gaskets.

Electrical Reliability:

Older wiring harnesses and components can degrade over time, leading to electrical gremlins. Proper insulation and connection maintenance are key.

Suspension Wear:

Duo-Glide suspension components (seals, bushings) can wear, affecting ride quality and handling.

📚 Vehicle History

Harley Davidson Legacy:

Harley-Davidson, founded in 1903, is an iconic American motorcycle manufacturer known for its V-twin engines and distinctive styling. The FL series represents their flagship large displacement touring motorcycles.

Fl Series Progression:

The Duo Glide is a direct descendant of the Hydra-Glide, introducing dual rear shocks and an improved front fork for enhanced ride quality. It preceded the Shovelhead engine adoption by a few years, though 1964 could be the transition year for some models.

Production Era:

The Duo-Glide model line generally ran from 1958 to 1964, with the 1964 model being the final iteration before the introduction of the Shovelhead engine.

🏆 Awards & Recognition

Model Recognition:

The Harley-Davidson Duo Glide is widely recognized as a cornerstone of American motorcycle history, celebrated for its blend of power, comfort, and iconic styling.

Vintage Motorcycle Appreciation:

Highly regarded by collectors and enthusiasts for its historical significance and classic V-twin performance.

Manual Certification:

This is a Factory Service Manual, directly produced by the manufacturer or under their authority, implying the highest level of accuracy and completeness for its intended purpose.