Harley-Davidson was founded in 1903 in Milwaukee, Wisconsin, by William S. Harley and the Davidson brothers. Over the following century it became one of the best-known American motorcycle manufacturers, building a lineup centered on large-displacement, air-cooled V-twin engines and a distinct riding character that has carried through generations of models.

The brand is known for its evolving V-twin engine families, including the Evolution engine of the 1980s and 1990s, the Twin Cam used from 1999 to 2017, and the Milwaukee-Eight introduced in 2017. Harley-Davidson also produced the liquid-cooled Revolution V-twin, co-developed with Porsche, for the V-Rod line from 2002 to 2017. Model lines have included the Sportster since 1957, along with Softail, Touring, Dyna models built until 2017, and the more recent Pan America adventure touring motorcycle introduced in 2021.

Manuals on this page cover the engine work needed for these platforms, including top-end and bottom-end service, transmission repair, electrical and wiring diagrams, torque specifications, and scheduled maintenance procedures. This gives technicians and owners the same level of detail used in factory service work.

Because Harley-Davidson engines have changed significantly across these different generations, having the correct manual for a specific engine family matters for accurate torque values, wiring layouts, and rebuild procedures. These resources benefit DIY owners performing their own maintenance, independent motorcycle shops, and restorers working on older Sportster, Softail, Touring, or Dyna models, as well as workshops servicing current Harley-Davidson motorcycles.