From WWII bomber to Grand Prix Winner, Triumph’s Twin was an incredibly flexible engine, blogs Stephen Cox. Triumph took the world by storm in 1938 with its its Speed Twin, the first of the great British parallel twin street motorcycles. But their enthusiasm – and sales – were cut short by World War II, which began the following September. Triumph engineers quickly adjusted to wartime production by re-designing the Speed Twin's excellent 500-cc power plant as a portable generator for milita...