1962 Triumph Bonneville

1962 Triumph Bonneville Background & History

The 1962 Triumph Bonneville was the culmination of a long line of Triumph vertical twins, starting with the 500cc 1938 Speed Twin. Designed by genius Edward Turner, it was the world’s first ‘modern’ vertical twin. It took the British motorcycle industry and the entire motorcycle market by storm and every other brand wanted one for themselves. But before they could do anything about it, Triumph did it again. One year after the launch of the game-changing Speed Twin, Triumph hot rodded their new twin and created a high-performance version of the bike called the Triumph T100 Tiger in 1939. World War 2 came along and put everything one hold until 1946, but when civilian production ramped back up Triumph was back in front and leading the way.

The 1962 Triumph Bonneville was a handsome machine, which certainly contributed to its success in the marketplace, along with its blistering performance.

By 1949, five competing brands, BSA, Ariel, Norton, Matchless/AJS and Royal Enfield, fielded their own 500cc vertical twins. No sooner than they got caught up, Triumph upped the ante again by boring and stroking its 500 twin out to 649cc and introduced it as the 1950 6T Thunderbird. Again, the industry was stunned, and once they recovered, once again put their noses to the grindstone to try to catch up. As all five punched out their own 500 twins, some built 600cc twin, some 650cc, and Royal Enfield even out-trumped Triumph with their 700cc Super Meteor. It didn’t help, Triumph just continued to forge new ground and lead the market in innovation and sales. In 1954 Triumph gave their new 650 twin the ‘Tiger-treatment’, ie: hotter cams, higher compression ratio and a bigger carburetor for more power. The result was the 1954 Triumph T110 Tiger and it was hot! Two years later, Triumph developed a new aluminum “Delta Head” that not only added more power but enhanced engine cooling. With it, a new bike was born, the 1956 Triumph TR6.

Up until this point, all these vertical twins, from all six brands producing them now, had used only one carburetor to feed both cylinders. This was made possible by the even firing pulses of the vertical twin, thanks to its 360-degree crankshaft. One carb worked well and kept things simple, and cheap. There is a saying in the motorcycle business that goes: “Too much is never enough.” Hence, if one carb is good, two would be better. Today putting two carbs on a twin-cylinder engine seems like an obvious improvement to make, but in 1959 it was revolutionary. Triumph reworked the Delta Head to accommodate two carbs, by splaying the intake ports outward instead of closer together and parallel as they were on the TR6. The result was the 1959 Triumph Bonneville.

The 1962 Triumph Bonneville was the last with non-unit construction.  Note how the engine and gearbox are separate items.  They are connected only by a third item, the primary chain case which is on the other side.

1962 Triumph Bonneville Details & Features

Once again, the Triumph Bonneville took the world by storm and Triumph wasted no time in setting several top speed records with the new bike, justifying the slogan “The Best Motorcycle in the World”, and until the Norton Atlas came out in 1962, the “Bonnie” was probably the fastest bike that money could buy. The 1959 model had a single down tube frame, but by 1960 they had adopted a twin down tube frame called the ‘Duplex Frame’. Problems with flexing around the steering head surfaced immediately under hard cornering. It took until 1961 for Triumph to figure out that the lack of a second frame tube running below the backbone (hidden by the tank) bracing the steering head was causing the problem. During the 1961 model year, the new frame member was added to all new bikes and retrofitted under warranty to all previous models with the Duplex frame, which stayed in circulation until the conversion of Triumph’s 650 line to unit-construction in 1963.

The 1962 Triumph Bonneville was pretty much carried over from 1961. They were mechanically nearly identical. One meaningful change was dedicating each fuel petcock to one carburetor, with a crossover line, and owners were encouraged to open both petcocks. It was found that under full throttle the carbs would starve for gas and the engine would stumble because enough fuel simply couldn’t be delivered at full throttle by just one petcock. The twin petcocks used to be used as a sort of ‘reserve’ feature, as one petcock had a one-inch tube that caused that side to run out of fuel sooner. The bike would stumble and the astute owner would switch on the other petcock which didn’t have the tube and so could drink the last inch of fuel, thereby warning the rider to get to a gas station pronto.

Edward Turner, creator of the vertical twin, was running Triumph by this time and he had great instincts when it came to style and detail, as seen here.

1962 Triumph Bonneville is an Icon

The 1962 Triumph Bonneville was, of course, the last model year with a non-unit construction engine and the now-retrofitted Duplex frame. By 1962, the Triumph Bonneville was well-developed and it was an impressive machine. The second carburetor certainly added some power, in actuality it added only 4 horsepower over the TR6, but what it really did was create an image and reputation for the bike that was bigger than life. The 1962 Triumph Bonneville was at the top of the heap with motorcycle buyers, but its presence went well beyond the motorcycle market. The Triumph Bonneville achieved a status that made the general public aware of it, even if they didn’t ride motorcycles. It was a true icon.

NON-UNIT vs UNIT CONSTRUCTION

LEFT: The 1962 Triumph Bonneville engine was of non-unit construction, meaning the engine, gearbox and primary chain case were all separate components held together by a set of brackets.

RIGHT:  In 1963 all Triumph 650s converted over to unit construction.  Note how the engine, gearbox and primary are now housed in a single, unitized case.

1962 Triumph Bonneville Specifications

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Triumph Bonneville Books

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