350 Bullet Royal Enfield

The Royal Enfield Bullet was originally a British overhead valve single cylinder 4-stroke motorcycle made by Royal Enfield in Redditch, West Midlands, but now produced by Royal Enfield Motors, the successor to the British company, at Chennai, Tamil Nadu in India. The Royal Enfield Bullet has the longest production run of any motorcycle having remained continuously in production since 1948. The Royal Enfield and Bullet names derive from the company's links with the Royal Small Arms Factory in Enfield.

During 2007 tighter European emission norms forced the Bullet Standard 350 to end 2007 as its last model year in the EU, so when on-hand stocks were all sold the British-design engined Bullet became no longer available new. All new models exclusively featured the AVL 'lean-burn' engine. The introduction of a 5-speed gearbox meant that Royal Enfield could 'fix' one of the long-standing quirks of the Bullet design—the foot-brake is on the left side while the gearshift is on the right. Accordingly, the Bullet Machismo 350 was equipped with this gearbox. However, the 'left-shift' gear-change provoked a backlash from Indian Bullet customers, forcing the company to not only continue the Bullet Standard with the traditional system, but even on the Electra it was offered only as an option, leading to the Electra 4-speed (traditional) and Electra 5-speed (left-shift) variants. Sales figures indicated that Indian Bullet customers had shunned the new gearbox, foregoing even the attraction of 5-speed transmission to keep the gearshift traditional.

As a result of work spanning several years, a new set of engines was introduced. These were the Unit Construction Engines (UCE). The 350 cc UCE found use in the domestic model Thunderbird TwinSpark in a configuration with two sparkplugs per cylinder, with integrated 5-speed left-shift gearbox. It has not been featured on any of the Bullet models, domestic or otherwise. As of 2011, the old cast-iron engine has been completely phased out, including in the Standard 350 model. Now all Royal Enfield bikes are only available with the all-aluminium UCE engine. Still, the old engine attracts its own following, most notably for the signature 'thump' it produces which is perceptibly louder than on the new bike.