From the factory brochure.
Triumph 1961 6T Thunderbird
"B" RANGE MODELS 650 C.C.
ENGINE 650 c.c. o.h.v., vertical twin with two gear-driven camshafts, Light alloy cylinder head, cast-iron barrel, high compression pistons, large bore carburetter. Splayed port head with two carburetters on T120, One-piece forged crankshaft with bolt on central flywheel. "Ef" section RB66 alloy connecting rods with plain big-ends. Dry sump lubrication with plunger type pump and pressure indicator. Gear-driven magneto with auto control. Thunderbird (6T) has A.G./D.G. lighting ignition system with emergency start circuit. Polished aluminium oil bath primary chain case. Air cleaner (not T120).
GEARBOX Triumph design and manufacture. Shafts and gears of hardened nickel and nickel-chrome steel - needle roller layshaft bearings. Positive stop footchange ("Slickshift" auto clutch operation on 6T and TUO). Multiplate clutch with indestructible cork sheet linings and rubber pad shock absorber. Accessible filler and level plugs and dual gearbox adjusters.
FRAME Brazed cradle type frame with twin front down tubes and swinging fork suspension, hydraulically damped and adjustable for varying loads. "Easylift" centre and prop stands (latter optional extra). Provision for anti-theft lock to steering head. -Front wheel stand.
FORKS Triumph design telescopic pattern with hydraulic two-way damping and steering damper.
FUEL TANKS Handsome large capacity all-steel welded petrol tank mounted on rubber and easily detached. Quick release fillers and plated parcel grid. Froth tower on oil tanks.
NACELLE 6T and T110 only (Patent No. $42670). Triumph design integral with top of forks enclosing headlamp, instruments and switchgear. Instruments internally illuminated,
BRAKES
Front: Full width hub, heavily finned, with efficient 8-in, diameter brake.
Rear: 7-in. diameter with cast-iron drum integral with chain sprocket. Fully floating shoes.
WHEELS AND MUDGUARDS Triumph design wheels with plated spokes and rims. Efficient front guard and stylish rear enclosure on 6T and T110.
LIGHTING EQUIPMENT Lucas alternator, crankshaft mounted, 12 a.h., battery, powerful headlamp (quickly detachable where nacelle not fitted) with combined reflector/front lens assembly, "pre-focus" bulb and adjustable rim. Wide angle rear/stop light with combined reflector.
SPEEDOMETER Smiths 120 m.p.h. (180 Km.p.h,) chronometric type with r.p.m., scale, internal illumination and trip recorder.
HANDLEBAR Chromium-plated with quick-action twist grip and adjustable friction control. Integral horn push Adjustable plated clutch and brake levers with built-in cable adjusters.
TWINSEAT Triumph design. Latex foam cushion covered in black waterproof "Vynide". Hinged on 6T and T110.
TOOLS Kit of good quality tools and tyre inflator, 192-page instruction Manual.
EXTRAS Prop stand all models. Pillion footrests all models. Quickly detachable rear wheel. (Wheel can be removed leaving brake, chain, etc. undisturbed.) Steering lock all models.
