| Specification | Data |
|---|---|
| Production Years | 2021 – Present |
| Engine Oil | SAE 20W50 (H-D 360 or Syn3) (3.8 L) |
| Tires (F/R) | 100/90B19 57H / 150/80B16 77H |
| Tire Pressure (F/R) | 2.07 bar (30 psi) / 2.76 bar (40 psi) |
| Battery Part No. | 66000207 |
| Spark Plug / Gap | 6R10 (0.76–0.89 mm) |
The Harley-Davidson FXBBS marks a significant engineering pivot in the Softail lineage. While previous iterations relied on the 107 cubic inch powerplant, the 2021 update introduced the Milwaukee-Eight 114 as standard, making the Street Bob the lightest Softail chassis equipped with the Motor Company’s high-torque performance engine. This power-to-weight ratio shift transformed the model from a budget entry-level cruiser into a formidable performance bobber.
Engineering Overview: The Milwaukee-Eight 114
At the heart of the FXBBS is the 1,868cc Milwaukee-Eight 114 V-Twin. This engine utilizes a four-valve per cylinder head design, which increases airflow and combustion efficiency over the older Twin Cam architectures. From a technical standpoint, the dual spark plugs per cylinder ensure more complete combustion, contributing to the 119 ft-lb of peak torque delivered at a low 3,000 RPM. This makes the FXBBS exceptionally responsive in city environments and aggressive in highway overtaking maneuvers.
Chassis and Suspension Dynamics
The Softail frame, redesigned in 2018, remains the backbone of the FXBBS. It maintains the classic hardtail aesthetic while utilizing a hidden monoshock rear suspension. The suspension features a high-performance front fork with Dual Bending Valve technology, which improves damping performance across a wide range of road surfaces. For technicians, it is worth noting that the rear preload adjustment is located beneath the seat, requiring a specific spanner wrench for optimal sag setup based on rider weight.
Maintenance Guide & Lab Specifications
Lubrication System
For the Milwaukee-Eight 114, thermal management is critical. We recommend SAE 20W50 oil. Harley-Davidson 360 Mineral is acceptable for break-in, but for high-temperature stability, Screamin’ Eagle Syn3 Full Synthetic is the lab’s preferred choice. Total capacity with a filter change is 3.8 Liters (4.0 US Quarts).
Ignition and Electrical
The FXBBS uses 6R10 spark plugs. Proper gapping is essential to prevent misfires and ensure the ion-sensing knock control system functions correctly. The gap must be set between 0.76–0.89 mm (0.030–0.035 in). The electrical system is supported by battery part 66000207, which provides the high cold-cranking amps (CCA) required to turn over the high-compression 114 pistons.
Wheel and Tire Integrity
The Street Bob runs a staggered setup with a 19-inch front and 16-inch rear. Maintaining 2.07 bar (30 psi) in the front and 2.76 bar (40 psi) in the rear is vital for both tire longevity and the specific ‘flickable’ handling characteristics this model is known for. Under-inflation in the rear tire will lead to sluggish turn-in and increased sidewall heat.
MotoSpecsLab Verdict
The FXBBS Street Bob 114 is a ‘purist’s machine’ that benefits from modern CAD-designed frames and high-output displacement. It requires disciplined maintenance—specifically regarding oil quality and tire pressures—to preserve its mechanical integrity. As a platform for customization, its technical foundation is among the most robust in the current Harley-Davidson lineup.