A cikin shekaru biyu masu zuwa, shi da abokinsa na ƙuruciya Arthur Davidson sun yi aiki a kan babur ɗin su ta amfani da shagon injin Milwaukee na arewa a gidan abokinsu Henry Melk. An gama shi a cikin 1903 tare da taimakon ɗan'uwan Arthur Walter Davidson. Bayan gwada babur ɗin su na lantarki, Harley da 'yan uwan Davidson sun gano cewa ba zai iya hawa kan tuddai a kusa da Milwaukee ba tare da taimakon pedal ba, kuma sun rubuta babur ɗin su na farko a matsayin gwaji mai mahimmanci.
shekaru biyu