1954 Triumph Speed Twin


1954 Triumph Speed Twin

1954 TRIUMPH SPEED TWIN BACKGROUND
In a few short years, the 5T Speed Twin went from being one of the world’s premium performance motorcycles to be Triumph’s entry-level twin. It had been surpassed by the T100 Tiger with its higher compression and hotter cams. And soon it would be bumped down still further when the 650cc 6T Thunderbird came out in 1950. And of course, the rest of the British motorcycle industry were also pushing out bigger and faster machines each year, so the competition was growing fierce. But for now, the ’54 Speed Twin was a solid seller, and while not the fastest thing on the road, its performance was adequate for the day.

1954 TRIUMPH SPEED TWIN DESIGN
The 500cc twin retained its cast iron cylinder block and head, and was fed by a single Amal carburetor. It was of non-unit construction, with the timing gear on the right, and the primary chain and clutch on the left, as usual. The 4-speed gearbox shifted with the right foot. The 1954 Triumph Speed Twin continued its use of the tried-and-true rigid frame, but offered a sprung rear hub as an option. The sprung hub used radially-positioned springs inside it to cushion the bumps. It was fine in theory, but tended to move in unintended ways when worn out or under extreme loads (ie: hard acceleration). It was a poor compromise solution, but one that made sense to Triumph at the time. It was a way to get some rear suspension while retaining their rigid frame, a very expensive thing to replace. The front end now had Triumph’s own telescopic forks with hydraulic damping. The previous year, the 1953 Speed Twin dropped its age-old magneto and generator in favor of a more modern alternator with a battery & coil ignition system. Many thought the old magnetos were more reliable than these ‘new-fangled alternators’, but two model years in, they’d proven to be as reliable as anything else Lucas ever made.


1954 Triumph Speed Twin SPECIFICATIONS

Model Designation
Engine Number prefix
Engine Type
Displacement
Bore & Stroke
Compression ratio
Carburetor
Engine output
Top Speed
Electrical system
Primary drive
Clutch
Gearbox
Final drive
Frame construction
Suspension, front
Suspension, rear
Brake, front
Brake, rear
Wheel, front
Wheel, rear
Wheelbase
Seat height
Ground clearance
Fuel capacity
Weight
Triumph 5T Speed Twin
47-5T
Air-cooled OHV vertical twin
498cc
63mm X 80mm
7.0:1
one- Amal 15/16″
28 bhp @ 6,000 rpm
85-90 mph
6-volt, Lucas magdyno, 40watt
Chain
Multi-plate, wet
4-speed constant mesh, right-foot shift
Chain
Steel tube, brazed lug
Telescopic
Rigid frame, sprung hub
7-inch SLS drum
7-inch SLS drum
3.25″ X 19.0″ Dunlop Universal
3.50″ X 19.0″ Dunlop Universal
54.0″
29.5″
6.0″
4 Imp gal
361 lbs, dry

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