This meant developing a new crankshaft and primary chaincase, which also provided the opportunity to add a Lucas alternator.

[1] In 1959 the G12 was redesigned and modernised as the De Luxe with a new full cradle tubular duplex frame and a new cylinder head.

While never as popular as rivals Triumph and BSA 650's in Open Class desert competition, the Matchless was powered by a torquey and reliable motor and was suspended with the superior Teledraulic front fork.

The Matchless G12 CSR designation officially stood for "Competition Sprung Roadster," the same nomenclature used with the G80 and G50 models.

The factory diverted Chief Engineer Jack Williams from AJS 7R development to address the problems with leaks and vibration and modify the bikes for racing, with the result that Ron Langston and Don Chapman won the prestigious Thruxton 500 long-distance endurance race on the AJS Model 31 counterpart to the G12.

If successful, this could have saved the company, as there was a huge demand in the US for powerful desert racers to compete in endurance events.