The location of the vehicle identification number on a Harley-Davidson depends on the model year, according to Harley-Performance.com. Prior to 1969, Harley-Davidson used the engine number as the VIN, which was located on the left side of the engine.
Between 1970 and 1980, Harley-Davidson started stamping the VIN on the frame and also the engines, with the exception of some motorcycles produced in 1979. Some of the motorcycles produced in 1979 had VIN numbers on the frame that did not match the engine, which had a crankcase number instead. In 1981, Harley-Davidson started using a 17-digit VIN on the frame and an abbreviated VIN on the engine.