In the mid-1970s, mechanical engineer Bill Davis designed and built a predecessor to the
Softail and patented the design in 1976. Davis sold his patents, prototype, and tooling to Harley-Davidson in January 1982. The Fat Boy was one of numerous Harley-Davidson models built on the Softail frame. • After 1994, the exhaust was made seamless. • In 1996 the
master cylinder and switch gear were revised. • In 1999 a new
Twin Cam engine for the 2000 model year was used. This necessitated a bespoke engine variant and changes to the frame. • In 2002 bullet-style indicators, alarm and immobilizer were added. • In 2005 a 15th Anniversary version was sold with a "Screamin' Eagle" engine, special paint and custom wheels. • The 2010 "Fat Boy Lo" FLSTFB had the lowest ever Harley seat height. The 2018 Softail frame has a modified swingarm with a Showa rear monoshock suspension mounted beneath the seat, replacing earlier twin shocks. So as to provide a more comfortable and better controlled ride with improved handling, the front forks contain a Showa "Dual Bending Valve" (SDBV), a cartridge simulator using two valves to control compression and rebound damping, giving linear damping characteristics proportional to fork stroke speed. Harley-Davidson claims the 2018 chassis is stiffer and lighter than earlier Softail and Dyna platforms. Further upgrades include an LED headlight and 18-inch "Lakester" rims, with wider 160mm front and 240mm rear tires. For 2020, the Fat Boy is only available with the Milwaukee-Eight 114 engine. Harley-Davidson also produced a 30th Anniversary edition for 2020. For 2025, the Fat Boy received an upgraded powertrain with the Milwaukee-Eight 117 engine, a reworked rear suspension, driver safety enhancements, and appearance updates including new wheels. A limited serialized run of 1990 35th anniversary Fat Boy Grey Ghost was released as part of the Icons collection with model code FLSTFI. The Grey Ghost pays homage to the original 1990 model with various cosmetic enhancements, including a round air intake, yellow rockers, tank concho, and an exclusive “Reflection” color scheme. It is one of Harley-Davidson's best selling models and has appeared prominently in a number of TV shows and movies. The Fat Boy earned a place in American pop culture after appearances in the movie
Terminator 2: Judgment Day. One of the motorcycles used in
Terminator 2 is displayed at the
Harley-Davidson Museum. It appeared again in
Terminator Genisys. ==See also==