Harley-Davidson Twin Cam engine

The Harley-Davidson Twin Cam are motorcycle engines made by Harley-Davidson from 1998 to 2017. Although these engines differed significantly from the Evolution engine, which in turn was derived from the series of single camshaft, overhead valve motors that were first released in 1936, they share a number of characteristics with nearly all previous Harley-Davidson engines. Both engines have two cylinders in a V-twin configuration at 45°, are air-cooled (some touring models use liquid cooling for the heads),^[1] and activate valves with push-rods. The crankshafts have a single pin with a knife and fork arrangement for the connecting rods. These are sandwiched between a pair of flywheels.

The Twin Cam 88 was a traditional design from Harley-Davidson, using two cams to drive the valvetrain, with the first being the famous '8-Valve' OHV V-twin racing models of 1915. Their 1920s single-cylinder models (the A, AA, BA, BB, and Peashooter) also used twin camshafts in the timing chest, and did their 1930s flathead engine models, like the VL and UL Big Twins, and the entire range of 45ci (750cc) V-twins from 1930 onwards: the Models D and W and their variants, such as the WLA military motorcycle and WR racing motorcycle.^[2]

The Twin Cam 88 was released for the 1999 model year in September 1998.^[3] The Twin Cam 96 was released for the 2007 model year.^[4]