| Specification | Data |
|---|---|
| Model Range | Harley-Davidson FAT BOY / FAT BOY SPECIAL (FLSTFB) (EURO 4) – FLSTF/17 |
| Production Years | 2010–2017 |
| Engine Oil | SAE 20W50 (2.8 L) |
| Front Tire | 140/75 R17 67V |
| Rear Tire | 200/55 R17 78V |
| Battery Type | 65989-97E |
| Spark Plug | 6R12 |
Engineering Highlight: The ‘Dark’ Evolution of the Softail
The Fat Boy Special (FLSTFB) represents a pivotal moment in Harley-Davidson’s engineering history. While the original Fat Boy was defined by its high-polish chrome, the Special variant introduced the ‘Satin Chrome’ and ‘Denim Black’ finishes. This wasn’t merely aesthetic; it was an engineering response to the growing demand for factory-custom ‘dark’ bikes that required specialized coating processes to ensure durability against the heat cycles of the massive Twin Cam engines.
Technical Performance & Powertrain
During the 2010–2017 production run, the FLSTFB transitioned through significant powertrain upgrades, most notably the shift from the Twin Cam 96B to the high-output Twin Cam 103B engine. As a ‘B’ designated engine, it features internal counterbalancers, allowing the engine to be rigid-mounted to the frame—providing that classic look while minimizing the vibration felt by the rider at highway speeds. The Euro 4 compliance in the later years of this range (FLSTF/17) necessitated precise EFI mapping to maintain torque curves while meeting stricter emissions standards.
Maintenance Guide & Essential Specs
Lubrication System
For optimal performance of the air-cooled V-Twin, SAE 20W50 oil is mandatory. The system requires 2.8 Liters. Given the high operating temperatures of the Euro 4 models, MotoSpecsLab recommends synthetic blends to prevent thermal breakdown during urban idling.
Tires and Contact Patch
The Fat Boy Special is famous for its massive rear profile. Maintaining correct pressures is critical for handling geometry:
- Front (140/75 R17 67V): 2.48 bar (36 psi)
- Rear (200/55 R17 78V): 2.90 bar (42 psi)
Under-inflation on the 200mm rear tire can lead to ‘heavy’ steering and premature cupping of the tread.
Electrical System
The FLSTFB utilizes the 65989-97E battery. Due to the high compression of the Twin Cam engine, ensuring a high Cold Cranking Amp (CCA) rating is essential for reliable starting. For ignition, the standard 6R12 spark plugs are the factory-recommended choice, providing the correct heat range to prevent pre-detonation.
MotoSpecsLab Verdict
The 2010–2017 Fat Boy Special remains a benchmark in the cruiser world. Its blend of traditional Softail geometry with modern fuel injection and ‘dark’ styling makes it a highly sought-after model for collectors and enthusiasts alike. Proper adherence to the 2.8L oil capacity and tire pressure specifications is the key to preserving the ride quality of this iconic machine.