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Triumph Twenty One

There are two schools of thought on the name ‘Triumph Twenty One’. It’s either honoring the 21st anniversary of Triumph Engineering, or was derived from the bike’s displacement in cubic inches. Either way, that was just it’s name. It’s model designation was 3TA, and it was Triumph’s entry-level 350 twin. At the time, these bikes were called middleweights in Britain (250s being lightweights, and 500s heavyweights), and it was a fairly substantial market for them in the day. At the time of its launch in 1957, these were used as basic transportation for legions of Brits when few could afford a car.

When the Triumph Twenty One was introduced in 1957, it was the first Triumph to employ ‘unit-construction’, a full two model years ahead of the 500 twins, and six years before the 650s. The 349cc vertical twin closely followed engine designer Edward Turner’s classic design, first seen in the 1937 Speed Twin with both pistons rising and falling together on a 360-degree crank. It rode on just two main bearings with a large, removable center flywheel. It had a cast iron cylinder block, alloy head with removable rocker boxes, and was fed by a single Amal Monobloc carburetor. There was a 4-speed constant-mesh gearbox with right-foot shift, fed by a primary chain drive and multi-plate wet clutch. It was set up very much like the 500 twin, except the 350 had a distributor sticking up at an angle on the timing side of the engine, driven by the intake cam gear. The 500 twins had two conventional sets of points like the 650s.

The styling of the Twenty One was heavily influenced by Britain’s home market, where the bikes were being used as commuters, in good weather or bad. And the when the weather was bad in Britain, it could be very bad. Mud, muck and road grime were constant problems over there, and in the late 1950s, there was a growing trend in British bikes toward fully-enclosed bodies. This made cleanup much easier, but also made repairs and routine maintenance more difficult. It was through at the time that this was the future of motorcycling, and many other British marques responded with similar offerings. The Velocette Vogue, the Norton Navigator Deluxe, even the Vincent Black Prince were all manifestations of this thinking. Triumph introduced the look on their 6T Thunderbird 650 line, the 5TA Speed Twin 500 and the 3TA Twenty-One 350. The bulky-looking fully-enclosed bikes were sarcastically dubbed “Bathtubs” by the public. When you see a Bathtub Triumph, you’ll know why they called them that.

The Triumph Twenty One continued in production alongside the 500 twins, until 1966 in 3TA form. The 350 twin continued on a few more years in a higher-performance version known as the T90, once again a scaled-down version of the T100 500 twin. The final year of 3TA production, 1966, was the only year the little 350 didn’t carry the bathtub bodywork.

Triumph Twenty One YEAR-BY-YEAR

1958 3TA Twenty One

2nd year for Twenty-One & for unit construction. “Bathtub”-styling.

1959 3TA Twenty One

Prominent “Bathtub”-bodywork not popular in the US, but much-needed in the rainy riding climate of Merry Olde England.

1960 3TA Twenty One

Triumph’s 350cc “Bathtub” twin soldiers into a new decade with few changes.

1961 3TA Twenty One

The 350cc 3TA was Triumph’s entry-level twin, tucked under the 5TA 500cc Speed Twin, which also shared the “Bathtub” bodywork that proved very unpopular in the US market.

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