| Specification | Data |
|---|---|
| Engine | Milwaukee-Eight 114 (1868cc) |
| Years Produced | 2018–Present |
| Oil Type / Capacity | SAE 20W50 / 4.3 L (4.5 qt) |
| Front Tire | 150/80-16 71H |
| Rear Tire | 180/70-16 77H |
| Tire Pressure (F/R) | 36 PSI / 42 PSI |
| Spark Plug | H-D 60100010 |
| Battery | 66000207 |
When Harley-Davidson unveiled the FXFBS Fat Bob in 2018, it represented the most aggressive engineering pivot in the company’s modern era. By merging the rigid, performance-oriented DNA of the discontinued Dyna line with the hidden-monoshock aesthetics of the Softail chassis, H-D created a ‘power cruiser’ that utilizes inverted front forks—an engineering choice typically reserved for sportbikes—to stabilize the massive 155 Nm of torque generated by the 114 Milwaukee-Eight engine.
Engineering Excellence: The Milwaukee-Eight 114
The heart of the FXFBS is the 114 cubic inch (1868cc) V-Twin. Unlike previous generations, this engine features a four-valve cylinder head design and dual spark plugs per cylinder (H-D 60100010), optimizing flame propagation and combustion efficiency. The counter-balanced design allows the engine to be rigidly mounted in the frame, which improves chassis stiffness without transferring excessive high-frequency vibration to the rider.
Maintenance & Service Specifications
To maintain the peak performance of the FXFBS, strict adherence to fluid and ignition specifications is mandatory. Our MotoSpecsLab technicians recommend the following:
- Lubrication: The system requires 4.3 Liters of SAE 20W50. For high-performance riding or extreme heat, synthetic fluids are preferred to prevent thermal breakdown of the 114’s high-torque components.
- Ignition: Use only the H-D 60100010 plugs. Given the high compression of the 114, incorrect heat ranges can lead to pre-detonation.
- Electrical: The 66000207 battery provides the high cold-cranking amps (CCA) necessary to turn over the heavy flywheels of the M8 engine.
Chassis and Handling
The Fat Bob is unique for its ‘chunky’ tire profile. The front 150/80-16 and rear 180/70-16 tires provide a massive contact patch. Maintaining the correct pressure—2.5 bar (36 psi) front and 2.9 bar (42 psi) rear—is critical. Under-inflation leads to heavy steering and uneven cupping of the front tread, while over-inflation compromises the damping effect of the high-sidewall tires.
FAQ
What is the recommended oil change interval?
While H-D suggests 5,000 miles, MotoSpecsLab recommends every 3,000 miles if used primarily for urban ‘stop-and-go’ riding to protect the Milwaukee-Eight’s top end.
Can I use non-OEM spark plugs?
It is highly recommended to stay with H-D 60100010 or a direct cross-referenced premium iridium plug to ensure the ION sensing knock-detection system functions correctly.