The 2006 FLSTFI Fat Boy is an iconic American cruiser, celebrated for its distinctive styling and the robust Twin Cam 88B engine. This model embodies classic design with its wide front fork, fat front tire, and ample chrome accents, appealing to riders who appreciate timeless aesthetics and reliable performance. Building on a rich heritage dating back to 1903, the company has consistently produced motorcycles that resonate with enthusiasts, and the Fat Boy, particularly the fuel-injected FLSTFI variant, has been a popular choice for its blend of heritage and modern engineering. This comprehensive workshop service repair manual provides in-depth guidance for the 2006 FLSTFI Fat Boy. It covers a wide range of essential topics, including detailed engine and transmission disassembly and assembly, fuel system servicing, electrical system diagnostics with wiring diagrams, brake and suspension maintenance, and frame and bodywork procedures. The manual is designed to assist owners, technicians, and mechanics with everything from routine scheduled maintenance, such as oil changes and tune-ups, to complex troubleshooting and complete component rebuilds, ensuring the longevity and optimal performance of the motorcycle.