The British-made Matchless G80, built by Associated Motorcycles, was a single cylinder 500cc motorcycle built between 1946 and 1966. In 1956, they changed the model from a long stroke to a short stroke with a bore of 86mm. By the 1950s, the G80 had an alloy cylinder head and the barrel fins went down to the base on the competitive models.
The motor on these bikes was originally released with a compression ratio of 5.9:1 due to poor quality fuel in the UK after World War II. In 1956, it was increased to 7.3:1. Due to this low compression, it was easy to kick-start these bikes and had better flexibility at low revs.