Harley-Davidson makes use of the code FLFB as a selected designation for its Fats Boy motorbike, a strong V-twin cruiser recognized for its commanding presence and fats tires. The letter “F” stands for the Huge Twin engine household, courting all the way in which again to 1941 and nonetheless going robust as we speak with the fashionable Milwaukee-Eight V-Twin engines. Harley says FL bikes use a 16-inch entrance wheel, which is the traditional wide-front look; FXST bikes use taller, thinner 19 or 21-inch fronts. Harley additionally launched its Hydra Glide hydraulic fork in 1949, the beginning of that traditional front-end fashion.
This “L” designation is completely different than the sportier “X” mannequin, which options thinner entrance wheels and a stripped-down look. The ultimate two letters, “FB,” merely imply that this particular mannequin is a Fats Boy. The Fats Boy was designed by Willie G. Davidson and Louie Netz and launched in 1990, turning into immediately recognizable for its muscular, vast look and iconic solid-cast aluminum disc wheels. The identify “Fats Boy” purely describes how broad and vast the motorbike appears whenever you see it head-on.
The massive change from FLSTF to FLFB
Harley-Davidson’s code designation for its Fats Boy wasn’t all the time FLFB, although. In 2018, the producer made its largest engineering change in 115 years, which led to the Fats Boy’s code switching from FLSTF to FLFB. Earlier than 2018, the letters “ST” in FLSTF stood for “Softail”, which referred to the bike’s particular hidden shock body design. Nevertheless, Harley utterly redesigned its complete cruiser platform that 12 months, making a body that’s stiffer but lighter. The model changed the outdated dual-shock system with a single hidden mono shock that is positioned proper beneath the seat, dramatically enhancing dealing with and efficiency.
Different enhancements that got here with the overhaul included changing your complete household of engines to realize considerably higher lean angles than earlier Softail or Dyna fashions. After 2018, Harley-Davidson’s Softail turned the cruiser platform, and all fashions in that line ran the brand new body with the hidden shock below the seat. The FLFB code is easier now, as a result of it focuses on what issues most: the Huge Twin engine (F) and traditional styling (L), whereas the superior body know-how is known to be customary throughout all of Harley’s trendy cruisers.
Efficiency variants and trendy know-how
Immediately’s FLFB fashions are critical machines with efficiency know-how that packs a punch regardless of their traditional look. The 2025 Harley-Davidson Fats Boy comes with the Milwaukee-Eight 117 Customized engine as customary, producing 126 lb-ft of torque at 3,000 rpm from its large 1,923cc (or 117-CI) motor. You might also see the code FLFBS; the “S” suffix simply implies that it got here with HD’s 114-CI engine. In 2018, the bottom FLFB had a 107-CI engine, whereas the FLFBS was geared up with a 114.
For 2025, many Softail fashions acquired a bump up from 114 to the Milwaukee-Eight 117, bringing extra energy and torque to these bikes. Moreover its uncooked energy, the fashionable FLFB has superior security options like Anti-lock Braking System (ABS), Cornering Enhanced Traction Management, and Tire Strain Monitoring. The 49mm entrance forks use dual-bending valve know-how for superior damping management, whereas the hidden rear monoshock contains a 43mm stroke with an adjustable hydraulic preload. Regardless of weighing 694 kilos, the redesigned chassis can obtain a powerful 25.6-degree lean angle, exhibiting off this classic-styled cruiser’s trendy efficiency.