Harley Davidson FLFB Fat Boy 2025 Service Manual

Cycle World's own framing places this squarely in Fat Boy history: launched in 1990, the Fat Boy quickly became an H-D icon, and the 2025 model marks a genuine engineering milestone — the first time the 117-cubic-inch Milwaukee-Eight has come standard on the base Fat Boy, previously reserved for CVO models and the Breakout. Cycle News reported the change delivers a full 7% more horsepower and 3% more torque than the outgoing 114.

The new Milwaukee-Eight 117 Custom delivers a claimed 104 hp at 4,800 rpm and 126 lb-ft of torque at 3,000 rpm — up from the 2024 model's 94 hp and 119 lb-ft — through new four-valve cylinder heads with revised combustion chamber shape, oval intake ports, and low-profile intake valve seats borrowed from the 2023/24 Grand American Touring and CVO engines. A frame-mounted oil cooler routes engine oil through the cylinder heads specifically to improve rider thermal comfort in low-speed traffic and hot weather, feeding a reworked two-into-two exhaust with lightweight muffler material tuned to emphasize low-frequency rumble over high-frequency noise.

For the first time, the Fat Boy comes standard with selectable Ride Modes (Sport, Road, Rain) and Harley's full Rider Safety Enhancements suite, including cornering-aware ABS and traction control — genuinely new territory for a model that's historically kept its tech minimal. Updated monoshock suspension improves comfort while staying firm under aggressive riding, and new hand controls accommodate cruise control alongside the added electronics. The signature silhouette carries forward unchanged in spirit: solid Lakester disc wheels, a 160/60R18 front and massive 240/40R18 rear tire, and the chrome-nacelle headlight that's defined the model since 1990. Styling refreshes include a new chrome tank medallion with a centered star and trailing wing, plus a two-tone Vivid Black/Whiskey Fire colorway. Dimensions run with a 30-degree rake and 65-inch wheelbase, shipping at roughly 668 lbs, and 2025 pricing started at $22,599.