- 650-cc parallel twin four-stroke - Engine Number: 6T11291NA Triumph introduced the Thunderbird in 1949 as the successor to the popular 500-cc Speed Twin. Withthe larger bore, the new 650-cc twin could reach speeds of up to 92 mph making it a more capable highway riding motorcycle. This is a classic example of a custom built 6TThunderbird with the strong and capable 650-cc engine. Custom paint, raked front end, and a number of custom parts make this a powerful and classic styled chopper, reminiscent of the 1970s styling. Sold with clear title. *Please note that this motorcycle has been in storage for the past few years and will requirerecommissioning prior to use.* *Reduced online buyer's premium of 15%*