1951 Triumph Thunderbird
The 1951 Triumph Thunderbird carried one model designation: "6T", and was known as the 6T Thunderbird, 6T or simply T-Bird. All 1951 Triumph Thunderbird 6T's were 650's & came equipped essentially the same, with the same rigid frame & sprung rear hub, and the same setup throughout. Unlike the later Triumph TR6
which came in a variety of flavors (ie: high pipes, low pipes, competition, etc.).
1951 TRIUMPH THUNDERBIRD - RIDING THE WAVE
The 1951 Triumph Thunderbird carried over largely unchanged from its 1950 model year introduction. There were the usual incremental improvements to engine & gearbox, mostly designed to improve reliability, ease vibration or simplify assembly. But Triumph Motorcycles & their ace designer Edward Turner, knew they had a hit on their hands & left things well enough alone with the 1951 Triumph Thunderbird. After all, don't fix it if it ain't broke.
1951 TRIUMPH THUNDERBIRD - OVERVIEW
On the 1951 Triumph Thunderbird, the Amal carburetor was increased in size from 1 inch to 1-1/16 inch. The 7-inch SLS front brake was also improved. The same brazed-lug rigid frame soldiered on with the notorious sprung rear hub trying to pass as rear suspension. It was an atrocious compromise implemented (indeed invented) by none other than Edward Turner himself as a way to delay the expensive retooling needed to adopt a more contemporary swing arm rear suspension. It was crude & ineffective. It didn't absorb bumps very well & looseness would develop in the hub leading to uncontrolled wheel movements & erratic handling as the result.1951 TRIUMPH THUNDERBIRD - COLOR SCHEMES
On a more positive note, the color scheme improved for the 1951 Triumph Thunderbird. Called Polychromatic Blue, it's a handsome metallic blue (pictured here). The Triumph T-Bird had its own logo, the so-called "Paper Dart" (unofficial nickname), pictured on the headlight nacelle above. This would later be cast into the primary cover.
The 1951 Triumph Thunderbird was a handsome machine in its day. The headlight nacelle of the 1951 Triumph Thunderbird incorporated the headlight, gauges (clocks), and handlebar mounts all in one neat package. This was a British innovation, intended to help keep the bikes clean in typically inclement British weather & also make them easy to clean, once ridden. The full fenders on this 1951 Triumph Thunderbird are also in keeping with that school of thought. It wasn't until the American Triumph dealers made a fuss that Triumph Motorcycles began to get lean & mean, starting with the 1956 Triumph TR6.
1951 Triumph Thunderbird SPECIFICATIONS
Bore & Stroke
Final drive sprockets
Air-cooled OHV vertical twin, non-unit
649cc / 40.0 ci
71mm X 82mm / 2.79" X 3.23"
8.5:1 (US & export); 7.0:1 (UK)
1- Amal Monobloc, 1-1/16"
34 bhp @ 6500 rpm
1/2" X .335" X 5/16" chain, 70 links
24T X 43T
4-speed constant mesh, right foot shift
5/8" X .400" X 3/8" chain, 101 links
18T X 46T
Brazed lug, rigid
Telescopic fork, hydraulic damping
Sprung rear hub, rigid frame
7" SLS drum
7" SLS drum
3.25" X 19"
3.50" X 19"
55.25" / 140.3 cm
31" / 77.5 cm
5" / 12.7 cm
3 Imp gal (US); 4 Imp gal (UK & export)
370 lbs / 168 kg
Check out these TRIUMPH BOOKS
TRIUMPH BONNEVILLE YEAR-BY-YEAR
TRIUMPH BONNEVILLE ESSENTIAL BUYER’S GUIDE
COMPLETE BOOK OF CLASSIC & MODERN TRIUMPHS
TRIUMPH MOTORCYCLES 1956-1983
FACTORY-ORIGINAL TRIUMPH TWINS
TRIUMPH MOTORCYCLE RESTORATION, PRE-UNIT
TALES OF TRIUMPHS & THE MERIDEN FACTORY
TRIUMPH ILLUSTRATED SHOP MANUAL, 1935-1939
TRIUMPH ILLUSTRATED SHOP MANUAL, 1937-1951
TRIUMPH ILLUSTRATED SHOP MANUAL, 1945-1955
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