The Royal Enfield Thunderbird is a cruiser style motorcycle produced by Royal Enfield Motors in India. It was introduced in 2000 with an AVL lean burn engine and five-speed gearbox. It is an Indian market model that has never been exported. In 2009, the AVL semi-unit engine was replaced with the new 346 cc unit construction engine(UCE).
The bike was renamed Thunderbird Twinspark owing to the twin sparkplugs in the UCE. Other parts have seen only minimal changes from the original Thunderbird. The final drive chain is moved to the right side and it is the most obvious change from the old model apart from the new engine.In October 2012, Royal Enfield launched the new 350 cc and 500 cc variants of the Thunderbird with a facelift.
It features front and rear disc brakes, a 20 L(4.4 imp gal; 5.3 US gal) teardrop shaped fuel tank, a split seat, digital speedometer console and fuel gauge, projector headlamps, LED tail lights and various cosmetic improvements over the 350 cc. Thunderbird 500 gets fuel injection system while Thunderbird 350 operates on carburetor.