<Tr> <Td> D - series (45 solo) </Td> <Td> 739 cc flathead </Td> <Td> 1929--1932 </Td> <Td> First H-D 45 cubic inch motorcycle, first H-D flathead V - twin motorcycle . </Td> </Tr> <Tr> <Td> R - series (45 solo: R, RL, RLD,) </Td> <Td> 739 cc flathead </Td> <Td> 1932--1936 </Td> <Td> Second series of 45 solo </Td> </Tr> <Tr> <Td> W - series (45 solo: W, WL, WLA, WLC, WLD, WR) </Td> <Td> 739 cc flathead </Td> <Td> 1937--1952 </Td> <Td> Recirculating oil system introduced on all H-D engines in 1936, R became W to denote this . WLA and WLC were military models, WR was a racing model </Td> </Tr> <Tr> <Td> Servi - Car </Td> <Td> 739 cc flathead </Td> <Td> 1932--1936 (R - series engine) <P> 1937--1973 (W - series engine) </P> </Td> <Td> Discontinued after 42 years in production . From 1964, the first Harley - Davidson to receive electric starting . </Td> </Tr>

Harley-davidson letter designation and a list harley model names