The first modern "over 500 c.c." vertical twin, the Thunderbird's vast capacity for hard work coupled with a modest petrol consumption has earned it an unequalled reputation among discriminating owners. Fast, smooth and powerful it is a joy to ride at all times.
ENGINES. 5T 500 c.c. : 6T 650 c.c. : Vertical twin cylinder O.H.V, with two gear-driven camshafts. Central flywheel. "H" section RR56 alloy connecting rods with patented plain big ends. Dry sump lubrication, high capacity plunger type pumps, pressure-fed big ends and valve gear. Highly polished timing cover fitted with oil pressure indicator. Patent air cleaner. Efficient barrel type silencers.
FOUR-SPEED GEARBOX. Triumph design and manufacture. Positive stop footchange. Shafts and gears of finest nickel and nickel-chrome steel. Large diameter multi-plate clutch with rubber pad type shock absorber. Polished aluminium primary chain case.
FUEL TANKS. All-steel welded tanks with quick-release caps and accessible filters.
FRAME. Brazed cradle type frame with swinging arm rear suspension with hydraulic damping instantly adjustable to varying loads. Also available to rigid frame specification.
FORKS. Triumph telescopic forks with hydraulic damping, Provide accurate steering with comfort at all speeds.
BRAKES. Exceptionally powerful with large diameter cast-iron drums. Finger adjustment.