Positioning:
The 1959 Duo Glide represents a pivotal era for Harley-Davidson, solidifying its reputation for robust, reliable, and iconic American motorcycles. This manual targets owners and mechanics dedicated to preserving or restoring these classic machines.
Competition:
In 1959, Harley-Davidson's primary competitors were Indian Motorcycles (though declining), and increasingly, European marques like Triumph, BSA, and Norton. The Duo Glide, with its Panhead engine and distinctive styling, offered a unique American V-twin experience.
Distinctive Features:
The Duo Glide (FL models) was characterized by its hydraulic front fork (Hydra-Glide) and rear suspension, offering a significant comfort improvement over earlier rigid or sprung-rear designs. The 1959 model year is particularly notable for its Panhead engine evolution.
Primary Coverage:
Repair, maintenance, adjustments, troubleshooting, disassembly, assembly, installation, and checking of all components.
Intended Audience:
Mechanics and DIY enthusiasts.
Estimated Page Count:
Detailed page count not provided in source, but typically service manuals of this era are comprehensive (e.g., 300-500+ pages).
Type:
Factory Service Manual / Repair Manual
Format:
Likely printed book format, potentially available digitally (PDF) by resellers.
Engine:
Complete engine disassembly, assembly, tuning, and repair procedures for the Panhead engine.
Transmission:
Service and repair of the 4-speed constant mesh transmission.
Electrical System:
Wiring diagrams, ignition system troubleshooting, lighting, charging system (generator), and battery.
Fuel System:
Carburetor (e.g., Linkert) service, fuel tank, and fuel lines.
Suspension:
Front fork (hydra-glide) and rear suspension (swingarm) maintenance and repair.
Brakes:
Drum brake system maintenance, adjustment, and repair.
Chassis Frame:
Frame inspection, repair, and alignment.
Bodywork Fenders:
Installation, removal, and adjustment of body panels, fenders, and tank.
Wheels Tires:
Wheel bearing service, spoke tensioning, and tire mounting/removal.
Maintenance:
Regularly scheduled maintenance tasks, lubrication, and fluid changes.
Troubleshooting:
Systematic diagnosis of common problems and their solutions.
Repair:
Detailed step-by-step instructions for repairing or replacing individual components.
Disassembly Assembly:
Complete guides for taking apart and putting back together major assemblies.
Installation:
Procedures for installing new parts or accessories.
Specifications Checks:
Verification of clearances, torques, and operational parameters.
Depth:
Comprehensive, covering everything from basic adjustments to full engine and transmission rebuilds.
Format Details:
If digital, typically a PDF with searchable text and clear image reproduction. If printed, high-quality paper stock.
Quality:
Expect clear diagrams, legible text, and durable binding for printed versions. Digital versions should offer high resolution.
Binding:
Likely saddle-stitched or perfect bound for printed manuals, designed for lay-flat use in a workshop environment.
Paper:
Durable paper stock resistant to workshop grease and oil, often with a matte finish to reduce glare.
Engine Type:
OHV V-twin, air-cooled 'Panhead'
Displacement:
73.74 cubic inches (1208 cc)
Bore X Stroke:
3.4375 in. x 4.000 in. (87.31 mm x 101.6 mm)
Compression Ratio:
Approximately 7.0:1
Horsepower:
Estimated 50-55 hp at 5,000 rpm (actual figures varied)
Torque:
Not typically stated in early manuals, but significant low-end torque characteristic of Harley V-twins.
Carburetor:
Linkert M-series carburetor (e.g., M74B)
Fuel Type:
Leaded gasoline, Octane rating typically 86-90 RON (research needed for specific recommendation)
Ignition Type:
Battery and Coil ignition with breaker points and condenser.
Oil System:
Total loss lubrication system (oil is injected into the crankcase and expelled).
Type:
4-speed, constant mesh, foot-shift, hand-clutch operation (later models offered foot-clutch/hand-shift options as well).
Options:
While foot-shift was standard for 1959, some earlier variations and custom builds might exist.
Clutch Type:
Dry, multi-plate clutch operated by handlebar lever.
Final Drive:
Chain drive, enclosed primary drive and rear chain.
Wheelbase:
Approximately 60.75 inches (1543 mm)
Length:
Approximately 86 inches (2184 mm)
Dry Weight:
Approximately 560-590 lbs (254-268 kg), depending on specific trim and accessories.
Fuel Capacity:
Approximately 4.0 US gallons (15.1 liters)
Safety Standards:
Motorcycles of this era were not subject to formal crash testing or safety rating systems as they are today. Safety features were mechanical and driver-controlled.
Braking System:
Drum brakes front and rear. Effective for the era but require consistent maintenance.
Lighting:
Headlight, taillight, brake light, and turn signals (where equipped).
Frame Design:
Robust steel frame providing a solid platform.
Oil Change Interval:
Typically every 1,000-1,500 miles (1600-2400 km), but the manual will provide exact specifications. Note the 'total loss' system.
Primary Chain Adjust:
Check and adjust primary chain tension as per manual's recommendations (e.g., every 2,000 miles).
Tune Up:
Includes spark plug replacement, ignition timing adjustment, and carburetor tuning, typically every 3,000-5,000 miles.
Engine Oil Type:
Motorcycle-specific oils with high zinc (ZDDP) content are recommended for flat-tappet engines. Viscosity typically SAE 50 or SAE 20W-50, depending on climate. Consult manual for exact type and capacity (approx. 4 pints/2 liters).
Transmission Oil Type:
Gear oil, typically SAE 80 or 90W. Capacity around 1 pint (0.5 liters).
Primary Chain Case Oil:
Shared engine oil, check level as per manual. Capacity is part of the engine oil system.
Fork Oil Type:
Specific fork oil viscosity, consult manual (often SAE 10W or similar).
Panhead Leaks:
Panhead engines are prone to oil leaks from various seals and gaskets due to age and design.
Carburetor Issues:
Linkert carburetors can require frequent adjustment and rebuilding due to wear and fuel degradation.
Ignition Timing:
Breaker points require periodic cleaning, gapping, and timing adjustments for optimal performance.
Brake Performance:
Drum brakes are less powerful than modern disc brakes and require diligent adjustment and maintenance.
Harley Davidson Legacy:
Founded in 1903, Harley-Davidson is an iconic American motorcycle manufacturer renowned for its V-twin engines, distinctive styling, and robust build quality. The brand has a deep-rooted history in performance, law enforcement, and popular culture.
Duo Glide Lineage:
The Duo Glide followed the Hydra-Glide, introduced in 1949. The 'Duo Glide' designation specifically refers to models with both front and rear suspension. The 1959 model is part of the 'Panhead' era (1948-1965) and a precursor to the Electra Glide.
Production Years:
The Duo Glide designation was used from approximately 1958 to 1964, preceding the Electra Glide.
Manufacturing Location:
Milwaukee, Wisconsin, USA
