| Specification | Data |
|---|---|
| Production Years | 2010-2017 |
| Engine Oil | SAE 20W50 (3.3 L) |
| Front Tire | 140/75R17 67V |
| Rear Tire | 200/55R17 78V |
| Spark Plug | Harley-Davidson 6R12 |
| Battery | 65989-97C |
Engineering Highlight: The Fat Boy Special (FLSTFB) represents a pivotal moment in Harley-Davidson’s Softail evolution. While the original Fat Boy was defined by its high-polish chrome, the ‘Special’ (or ‘Lo’ in North American markets) introduced the “Dark Custom” aesthetic to the heavyweight cruiser segment. Specifically, the FLSTFB featured a lowered suspension—dropping the seat height to a mere 24.25 inches—making it one of the lowest production motorcycles ever offered by the Milwaukee firm, significantly altering the center of gravity for improved low-speed handling.
Technical Analysis & Performance
The 2010-2017 FLSTFB utilizes the Twin Cam 96B or 103B counter-balanced engines. Unlike the rubber-mounted engines in the Touring line, the ‘B’ designation signifies internal counter-balancers that allow the engine to be rigid-mounted to the frame, providing that signature ‘connected’ feel without the excessive vibration that would otherwise fatigue the rider over long distances.
Maintenance Guide
Lubrication System
For optimal thermal stability and shear resistance, MotoSpecsLab recommends SAE 20W50. The system requires 3.3 Liters. While H-D 360 Mineral oil is sufficient, the Screamin’ Eagle SYN3 Full Synthetic is preferred for high-ambient temperature environments to protect the rear cylinder from heat soak.
Chassis and Contact Patch
The FLSTFB’s handling is dictated by its massive 200mm rear tire. Maintaining precise pressure is critical to prevent “cupping” and ensure linear turn-in.
- Front: 2.48 bar (36 psi)
- Rear: 2.90 bar (42 psi)
Failure to maintain the rear 42 psi can lead to sluggish handling and premature wear of the 78V rated carcass.
Electrical & Ignition
The ignition system relies on Harley-Davidson 6R12 plugs. Gapping should be checked every 5,000 miles. For starting reliability, the 65989-97C battery provides the high cold-cranking amps (CCA) necessary to turn over the high-compression V-twin pistons.
FAQ
Q: How often should I change the primary chaincase lubricant?
A: While the engine oil is changed every 5,000 miles, the primary lubricant should typically be inspected at the same interval and changed every 10,000 miles under normal operating conditions.
Q: What is the benefit of the 200mm rear tire on the FLSTFB?
A: Beyond the aggressive aesthetic, the wide contact patch provides significant straight-line stability and traction for the high-torque Twin Cam engine.