Brand: Harley-Davidson
Model: W-series (45 solo: W, WL, WLA, WLC, WLD, WR)
Years: 1937–1952
Engine: 45.1 cu in (739 cc) flathead
Notes: 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
Source: Wikipedia