Saturday, January 8, 2022

ABC 400cc flat twin

A couple of photos of an ABC flat twin. The ABC was a Granville Bradshaw designed bike that was manufactured by the aero company Sopwith.

A typically Bradshaw design, the ABC was both futuristic and flawed. The bike featured leaf spring rear suspension at a time when most bikes were rigid. The motor was a 400cc ohv flat twin but the valve gear was a notable weakness and several different brands of after-market improved valve gear appeared soon after the bike's introduction. With standard valve gear the bike was notorious for shooting pushrods out on a horizontal plane.

The 400cc ABC was a limited success with the buying public and was made from 1919 to 1923. The demand for a small, expensive and sophisticated machine was limited in a conservative market. The peculiar fact that Bradshaw designed the bike without a kickstart and that it had to be paddled off to start cannot have helped.

The design was licensed out to Gnome et Rhone in France who had a connection with Sopwith as fellow aviation manufacturers. The Gnome et Rhone version received several improvements (strengthened valve gear, a kickstart and a boost to 500cc) but was also not a big seller and made only from 1920 to 1924.

ABC flat twin. The very dropped bars are slightly
incongruous with footboards and legshields.

The ABC was a luxury machine so it is fitting
to see it in the garden of an upmarket house.
A small dog's butt has cheekily crept in to the picture!


  1. Not a handsome looking motorcycle overall. Wouldn't the leg shields have perfectly blocked the cooling airflow? The exhaust pipe outlet looks like a miniature; nothing shiny to boast of power (I realize the silencer is a separate can). But I do like the placement of the bulb horn, facing down, implying, like the drop bars, a sporting accommodation.

    1. They are better looking in the flesh.
      The legshield is actually open in front of the cylinders so, of their various issues, overheating was not one.
      These points you make are probably close to the reasons they didn't sell many of them in the first place!