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Triumph Trident


Triumph Trident
Image courtesy of: classic-motorbikes.net

In the late 60s, the British motorcycle manufacturers were struggling. Aging models, poor management, and massive competition for their small engined bikes from both Europe and Japan was taking its toll. So good were many of the 250s being imported from Japan that they were almost equal on performance with many of the British bikes of the time, and cost considerably less too.

One of the longest serving British manufacturers, Triumph, had seen many difficult times, including being sold to one of its competitors, BSA, by the previous owner, Jack Sangster in 1951. By 1965, Triumph and BSA had become fully merged, bringing their production lines together.

More Power

By 1959, Triumph had modified their original vertical twin to its ultimate size of 650-cc’s, for the Bonneville. The original 500 vertical twin engines (5T Speed Twin) introduced in 1946, had been modified to create the more powerful Tiger 100 then again by changing the stroke and bore to give 649-cc, in an attempt to get even more power out of the original engine design. The result was the 6T Thunderbird which first appeared in 1950.

In 1959 the most famous of Triumph’s motorcycles was produced: the Bonneville. Although the new machine was an instant success, the company knew that something different from the vertical twin concept was needed. The biggest problem for the twin was the engine’s inherent balance and vibration problem (counter balance shafts had not been invented at that time).

In 1962/3, realizing there was only a finite amount of power available from the aging twin design before vibration became too bad, designers Bert Hopwood and Doug Hele started a design and prototype run for a new three cylinder machine. The new engine would have its crank pins oriented at 120 degree intervals in an attempt to reduce vibration.

Management Delays

By 1966 the new machine, the Triumph Trident, was close to being ready for production. Unfortunately, management differences between Triumph and BSA caused a delay, primarily because BSA wanted a similar three cylinder machine but at the same time sufficiently different to be recognized as a BSA. One substantial change the BSA board wanted was for the cylinders to be inclined 15 degrees forward.

This requirement by the BSA management delayed the introduction of both the Trident and the Rocket-3, which the new BSA was to be named, until 1969.

The Triumph Trident (T150)

The Trident finally hit the show room floors in 1969; the company producing more than 19,000 units before production ceased in 1975.

Specification for the 1969 Trident included:

  • Engine: Air cooled, transverse three cylinder 4-stroke, push-rod OHV, 2-valves per cylinder
  • Capacity: 741-cc (Bore 67-mm, stroke 70.5-mm)
  • Compression ratio: 9.5:1
  • Carburation: Three 26mm Amal MK1’s
  • Ignition: Battery powered contact points
  • Claimed HP: 58 at 7250 rpm
  • Transmission: 4-speed sequential, chain final drive
  • Forks: Telescopic
  • Rear Shocks: Dual coil-over spring over with metal shrouds
  • Brakes: Internal expanding drum front and rear (twin leading shoe front, single rear)
  • Tires: 4.10 x 19 Front and rear
  • Dry weight: 458 lb’s. (208 kg’s.) dry
  • Top speed: 115 to 120 mph

Major modifications included a change to a 5-speed gearbox which first appeared on the 1972 Trident. This conversion is available to early 4-speed Tridents from companies such as Rob North. However, these machines benefit greatly by converting them to fully electronic ignitions. Systems are available from Boyer Bransden and Pazon.

Although the Tridents are generally reliable, they need to be kept in tune. This is particularly true where the carbs are concerned. Not only do the carbs need to be synchronized regularly, they also need to have their float heights checked.

Note: If the float level on the Amal carbs is too high, it can cause flooding and richness which can remove (wash off) lubrication from the cylinder walls result in excessive wear and oil burning.

An early example in good condition is valued at around $11,000.

Further Reading

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