LIVELY LIGHTWEIGHTS

While BSA, Ariel, Velocette, AJS Matchless and others supplied only single-cylinder machines for the postwar 350 market, Norton and Triumph tried something different with their interpretations of middleweight (as they were back then!) twins. Sixty years later, those middleweight 350s have become lightweights, and their compact dimensions, ease of starting and peppy performance lend themselves very well to the role of the classic motorcycle.

Triumph announced their first unit twin in 1957, as a follow-up to the 3T preunit 350 rigid and optional sprung hub models. Initially, the new twin was known as the Triumph ‘Twenty-one’, to celebrate twenty-one years since Jack Sangster had formed the Triumph Engineering Company when motorcycle and automobile divisions parted company in 1936. The 350 unit twin adopted its 3TA moniker the following year, the same year that Triumph introduced the 5TA that would outshine its baby sibling in time.

The 3TA earned Triumph valuable contracts with police and other services throughout the UK and the Commonwealth. In 1960 the police 3TA was fitted with an electric starter, but sadly this was not adopted on civilian models. Unlike the earlier pre-unit twins, the 3TA featured the unpopular bathtub rear enclosure introduced along with heavier, fluted mudguards as well as Triumph’s attractive headlamp nacelle. In 1962 the sportier Tiger 90 was introduced, with an improved 349cc engine, updated paintwork, slimmeddown mudguards, chrome Lucas headlamp, attractive two-tone dualseat and a partially-enclosed bathtub.

The bathtub enclosure was soon dropped due to its unpopularity in the UK – many were simply binned as fashion dictated. Unfortunately sales of the lightweight 350 were already in decline and the 3TA ceased production in 1966, followed by the Tiger 90 in 1968. Today Triumph 350/500cc bathtub models are highly-prized classics.

The 3TA (T90 in brackets) was produced between 1957-66 (1962-68) and the new unit construction engine had a bore and stroke of 58.25 x 65.5mm (ditto T90), with a compression ratio of 7.5:1 (9.0:1) and displacing 349cc (ditto T90). Power output was a conservative 18.5bhp @ 6500rpm (27bhp @ 7500rpm). Standard gearbox sprocket was 18T (17T) and rear wheel was 43T (46T). The 3TA was fitted with 17-inch rims (18-inch) and 7-inch (ditto T90) drum brakes front and rear. The petrol tank held 3.5 gallons (3 gallons) of fuel. Dry weight was 340lb (336lb). Electrics were 6V alternator and coil ignition, changing to a 12V system in 1966.

Although Triumph tried hard to produce a modern-looking, civilised space-age motorcycle, many riders preferred a less modern, less civilised machine, hence the Tiger 90

Hindsight is too often obscured by the smokescreen of history. Imagine the surprise the appearance of the new 350 twin must have caused when it appeared pp in the late 1950s