 The now-oversquare modified engine used the 650 Bonneville twin-carb cylinder head having bigger valves, ports and carburettors than a standard Triumph 500, allowing for efficient air-fuel intake at racing speeds.The 650-size crank journals and main bearings were larger than a 500 which allowed for greater reliability.When track-testing the 500, "Motorcycle Mechanics" editor John Houslander reported that the engine would safely rev to 9,000 rpm making a potential 50 bhp and – with Isle of Man gearing and a four-speed gearbox – a top speed of was likely.