🏷️ Basic Information

Make:

Harley-Davidson

Model:

FLSTF Fat Boy

Year:

2015

Model Code:

FLSTF

👋 Introduction

Market Position:

The Harley-Davidson FLSTF Fat Boy represents a premium cruiser motorcycle known for its iconic styling, comfortable ride, and V-twin performance, targeting riders who appreciate classic American motorcycle aesthetics and a robust riding experience. It holds a significant position in the cruiser segment.

Competitive Analysis:

Competes with other large-displacement cruiser motorcycles from brands like Indian Motorcycle, Victory Motorcycles (prior to discontinuation), and some Japanese manufacturers offering V-twin cruisers in similar displacement classes. The Fat Boy's distinctive styling and brand heritage are key differentiators.

Key Features:

Iconic retro styling with chrome accents, comfortable ergonomics for long-distance riding, powerful Twin Cam 103 engine, robust braking system, and Harley-Davidson's renowned brand cachet and customization potential.

📋 Manual Details

Systems Covered:

Engine, Transmission, Clutch, Primary Drive, Fuel System, Electrical System, Chassis, Suspension, Brakes, Wheels, Tires, Bodywork, Controls, Diagnostics

Page Count:

Refer to actual product; estimated 600-800 pages typical for factory service manuals.

Manual Type:

Factory Service Manual / Repair Manual

Language:

English

Format:

Electronic (PDF)

📖 Manual Coverage

Engine System:

Twin Cam 103 (1690cc) Engine: Disassembly, assembly, inspection, troubleshooting, overhaul of top end (cylinders, pistons, heads), bottom end (crankshaft, connecting rods, bearings), valve train, timing, lubrication system, cooling system (air-cooled), fuel injection system (EFI).

Transmission System:

6-Speed Cruise Drive Transmission: Gearbox disassembly, assembly, inspection, troubleshooting, clutch operation and service, primary drive chain tensioning and inspection.

Electrical System:

Wiring diagrams, charging system (alternator, regulator), ignition system (ignition module, spark plugs), starting system (starter motor), lighting system (headlights, taillights, turn signals), instrumentation, sensors, EFI control unit (ECU) diagnostics.

Chassis Suspension Brakes:

Frame, front fork (telescopic, gaiter-covered), rear suspension (shock absorbers), wheel bearings, steering assembly, front and rear brake systems (calipers, rotors, master cylinders, brake fluid), ABS integration (if equipped).

Maintenance Procedures:

Routine maintenance checks, oil and filter changes, air filter replacement, spark plug replacement, brake fluid flush, clutch adjustment, belt drive inspection and adjustment, chassis lubrication, battery maintenance.

Repair Procedures:

Complete engine overhaul, transmission rebuild, suspension component replacement, brake system repair, electrical component diagnostics and replacement, body panel removal and installation, exhaust system service.

Troubleshooting Guides:

Diagnostic flowcharts and procedures for common issues related to engine performance, electrical faults, starting problems, braking issues, and chassis malfunctions.

Technical Depth:

Comprehensive factory-level detail including torque specifications, special tool requirements, diagnostic trouble codes (DTCs), electrical schematics, and step-by-step repair instructions suitable for professional technicians and experienced DIY enthusiasts.

📊 Manual Specifications

File Format:

PDF

Print Quality:

High-resolution, clear and legible text and diagrams for easy printing.

Binding Type:

N/A (Electronic Format)

Paper Type:

N/A (Electronic Format)

⚙️ Engine Specifications

Engine Type:

Air-cooled, Twin Cam 103B (B for Balanced Shaft)

Displacement:

1690 cc (103 cubic inches)

Bore X Stroke:

3.875 in. x 4.38 in. (98.4 mm x 111.3 mm)

Compression Ratio:

9.6:1

Valvetrain:

Overhead valves (OHV), 2 valves per cylinder, pushrod actuated.

Horsepower:

Approximately 70-75 HP (claimed, may vary by specific tuning and emissions).

Torque:

Approximately 99.0 lb-ft @ 3500 rpm (134 Nm).

Fuel Delivery:

Electronic Sequential Port Fuel Injection (ESPFI)

Fuel Type:

91 octane (R+M)/2 or higher recommended.

Oil Type:

Harley-Davidson Genuine V-Twin 20W-50 SYN3 (or equivalent API CG-4 or higher).

Oil Capacity:

3.0 US qt. (2.8 L) with filter change.

🔧 Transmission

Transmission Type:

6-Speed Cruise Drive

Gear Ratios:

1st: 9.312, 2nd: 6.955, 3rd: 4.765, 4th: 3.788, 5th: 3.225, 6th: 2.790

Primary Drive:

Chain, 34/46 ratio

Final Drive:

Belt, 32/66 ratio

Clutch Type:

Hydraulically actuated, multi-plate wet clutch.

Transmission Fluid Type:

Harley-Davidson Formula+ (or equivalent API GL-4).

Transmission Fluid Capacity:

2.7 US qt. (2.5 L)

📐 Dimensions

Length:

93.5 in. (2375 mm)

Seat Height Laden:

26.0 in. (660 mm)

Ground Clearance:

4.7 in. (119 mm)

Rake:

32 degrees

Trail:

5.2 in. (132 mm)

Dry Weight:

691 lb (313 kg)

Weight In Running Order:

721 lb (327 kg)

Gross Vehicle Weight Rating:

1261 lb (572 kg)

Fuel Capacity:

5.0 US gal. (18.9 L)

🛡️ Safety Features

Safety Ratings:

Not typically rated by agencies like NHTSA or IIHS as it's a motorcycle. Safety is primarily derived from rider skill and adherence to maintenance.

Braking System:

Hydraulic disc brakes front and rear. Optional Anti-lock Braking System (ABS) available on some models.

Lighting:

Halogen headlight, LED taillight and brake light, amber incandescent turn signals.

Chassis Construction:

Steel frame and swingarm contribute to stability and rider confidence.

💡 Technology Features

Infotainment System:

Standard models may not feature advanced infotainment. Typically equipped with a speedometer, tachometer, fuel gauge, and indicator lights. Some may have provisions for aftermarket audio systems.

Driver Assistance Features:

ABS is an optional feature. Cruise control is typically not standard on the FLSTF Fat Boy models of this era.

Connectivity Features:

No integrated smartphone connectivity (e.g., Apple CarPlay, Android Auto) on this model year.

Diagnostic Capabilities:

Features on-board diagnostics that can be accessed via a diagnostic port using a Harley-Davidson Digital Technician or compatible scan tool to retrieve Diagnostic Trouble Codes (DTCs).

🔧 Maintenance

First Service:

1,000 miles (1,600 km) or 6 months, whichever comes first.

Subsequent Services:

Every 5,000 miles (8,000 km) or 12 months, whichever comes first.

Engine Oil Spec:

Harley-Davidson Genuine V-Twin 20W-50 SYN3 or equivalent API CG-4 or higher.

Transmission Oil Spec:

Harley-Davidson Formula+ or equivalent API GL-4.

Primary Chain Case Oil Spec:

Harley-Davidson Formula+ or equivalent API GL-4.

Brake Fluid Spec:

DOT 4 (Harley-Davidson recommends their own brand or an equivalent).

Common Issues:

Some owners report potential issues with the hydraulic clutch actuation, belt drive wear, and early Twin Cam engine models sometimes experiencing oil leaks or top-end noise if not properly maintained. Electrical gremlins can occasionally occur, but are often manageable with proper diagnostics. Clutch hub nut recall was issued for some 2015 models.

Oil Filter Part Number:

Harley-Davidson OEM 63796-77A (or equivalent aftermarket, e.g., Screamin' Eagle 25400006).

Air Filter Part Number:

Harley-Davidson OEM 29000004 (or equivalent aftermarket).

📚 Vehicle History

Brand Heritage:

Harley-Davidson boasts a long and storied history, originating in Milwaukee, Wisconsin, in 1903. It is synonymous with American motorcycle culture and iconic designs.

Model Evolution:

The Fat Boy model was introduced in 1990 and quickly became an icon, known for its distinctive styling reminiscent of pre-WWII motorcycles. It has evolved over the years, incorporating modern technologies while retaining its classic appeal. The 2015 model features the Twin Cam 103 engine and a 6-speed transmission.

Production Location:

Primarily manufactured at Harley-Davidson's York, Pennsylvania, and Kansas City, Missouri, plants.

🏆 Awards & Recognition

Recognitions:

The Fat Boy has consistently received praise for its iconic design and comfortable riding experience. While specific awards for the 2015 model year might not be widely publicized, the Fat Boy lineage is a recognized standard in the cruiser motorcycle market for its styling and performance.