According to wikipedia:
The Scout was introduced in 1920 with a 596 cc (37ci) engine. The engine size was increased to 745 cc (45ci) in 1927 in response to the popularity of the Excelsior Super X.[1][2]
In the 1950s(whether WiKi knows it or not)the Scout was a 500 CC machine, intended to compete with the British bikes of the day. I inadvertently typed 250 CC. I had a Scout frame and a friend of mine put a 60 Cubic Inch Harley in one, it was a he** of a bike, a one of a kind as far as I know.