The 1951 Triumph Thunderbird carried the model designation “6T”. All 6T’s were 650’s & came equipped essentially the same, with the same rigid frame & sprung rear hub, and the same setup throughout.

For 1970, the Triumph TR6 was again known as “Tiger”, as the single carb twin would continue to be known, even beyond the switch from 650 to 750. But for the 1970 model year, there were 4 models in ...