Introduced in 1931 as a four-stroke single cylinder motorcycle, this model was the first to feature the Bullet name. It differed in a number of ways from its successors (which are now familiar): it had an inclined engine with exposed valve gear featuring four valves per cylinder with 350 cc and 500 cc options. In 1933, a 250 cc option was also added to the range.[3] Its frame was also considerably different, having centre-spring girder front forks, being among a new range of models from Royal Enfield that featured them, along with a saddle-type fuel tank