| Component | Specification |
|---|---|
| Model Years | 2018–2019 |
| Engine | Milwaukee-Eight 107 (1745cc) |
| Oil Type / Capacity | SAE 20W-50 / 4.7 Liters |
| Front Tire | 150/80-16 71H |
| Rear Tire | 180/70B16 77H |
| Tire Pressure (F/R) | 36 psi (2.5 bar) / 40 psi (2.8 bar) |
| Battery Part Number | 66000207 |
| Spark Plug | Harley-Davidson 6R10 |
The 2018 debut of the FXFB Fat Bob represented a watershed moment in Harley-Davidson’s engineering history. It was the flagship of the unified Softail platform, effectively killing the Dyna line by integrating a hidden rear monoshock into a frame that is 34% stiffer than its predecessor. This specific iteration, the 107 CUI Milwaukee-Eight, is praised by technicians for its balance of thermal efficiency and torque delivery, utilizing dual spark plugs and four-valve heads to optimize combustion.
Engineering Analysis: The Softail Revolution
The FXFB’s chassis geometry was designed to solve the traditional cruiser dilemma: stability vs. agility. With an inverted front fork and a dual-disc braking system, the Fat Bob 107 was the first Softail to offer sport-touring levels of front-end feedback. The Milwaukee-Eight 107 engine provides 145 Nm of torque, peaking early in the RPM range, which demands high-quality lubrication to manage the heat generated by its high-compression cylinders.
Maintenance Essentials & Fluids
For the FXFB to maintain peak performance, oil management is critical. The system requires 4.7 liters of SAE 20W-50. Given the air/oil-cooled nature of the 107 engine, synthetic fluids are highly recommended for riders in warmer climates to prevent viscosity breakdown. The Harley-Davidson 6R10 spark plugs should be inspected every 5,000 miles for carbon fouling, a common occurrence if the bike is used primarily for short city commutes.
Tires and Handling
The Fat Bob is distinctive for its ‘fat’ tire profile. It utilizes a 150/80-16 front and a 180/70B16 rear. Maintaining the precise pressure of 36 psi (front) and 40 psi (rear) is non-negotiable; even a 3-psi drop can lead to heavy steering and uneven cupping on the aggressive tread pattern. The 66000207 battery provides the high cold-cranking amps (CCA) necessary to turn over the large-displacement V-twin reliably.
Frequently Asked Questions
How often should I change the oil?
While the manual suggests longer intervals, MotoSpecsLab recommends changing the 4.7L of 20W-50 every 5,000 miles or annually to protect the Milwaukee-Eight valvetrain.
What makes the FXFB different from the FXFBS?
The FXFB features the 107 cubic inch engine, whereas the FXFBS features the 114. The 107 is often preferred by long-distance riders for its slightly smoother power delivery and cooler operating temperatures.