Enfield Thunderbird TwinSpark

To 2003. The thunderbird was first introduced

With a 350 cc AVL lean burn aluminium engine and a five-speed gearbox with the gear shifter on the left side. It is also the first Royal Enfield to be fitted with a constant vacuum MIKUNI-UCAL Carburettor in stock condition from the company. To 2002 (approx less than 2 years), where as, the 5-speed AVL aluminum engines with left-side gear shifter were produced

To 2020. The Royal Enfield Thunderbird is known as Royal Enfield Rumbler in export markets. To 2009 (approx less than 7 years). This makes the Royal Enfield AVL engines rare and quite the collector's item. To 2005. These consisted of CDI only as part of its electricals.

To 2009. These consisted of CDI+TCI as part of its electricals.

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.