Routt Big Bore Kit for 650cc 9 Stud Models. Kit consists of Big Bore Barrel, 8.9:1 Cast pistons (Complete with rings, gudgeon pins, circlips) and a copper head gasket. Suitable for Triumph T120 Bonneville / TR6 Trophy 6T Thunderbird 1963-74 plus any other Pre Unit 650 when using a 9 stud head. Great for Tritons and Cafe Racers.The item "Routt Big Bore Kit Triumph T120 Bonneville / TR6 Trophy / 6T Thunderbird" is in sale since Thursday, February 23, 2017. This item is in the category "Vehicle Parts & Accessories\Motorcycle Parts\Engines & Engine Parts\Cylinder Barrels". The seller is "britishbikebits" and is located in Ashby de la Zouch. This item can be shipped worldwide.