1957 Triumph Twenty-One — Number 1

A classic motorcycle enthusiast could labor several years attempting to track down a rare and historically important machine. It was a different story for Bill Sevier, although the Texan doesn’t consider himself a “true” classic aficionado. And when he bought this 1957 Triumph Twenty-One, he didn’t quite realize the significance of what he’d found.

His connection to this Triumph began when he was working for Shell. In the early 2000s, he’d been sent from his home in Houston, Texas, to work in the Netherlands. Around 2013, Bill’s elderly neighbor in Wassenaar, near The Hague, asked if he’d be interested in buying a motorcycle. “He had this bike sitting in his backyard that he wanted to show me,” Bill recalls. “It was killing him that it was just sitting there, covered in a tarp, and his kids didn’t want it. So, he said to me, ‘Would you do something with it?’ And I thought, well, I could give it a shot.”

What Bill ended up taking a shot on was the very first larger bore unit-construction Triumph motorcycle to roll out of the company’s Meriden factory — a 1957 Twenty-One, or 3TA, with serial number H1. The 350cc machine, together with H2, the next Twenty-One off the line, was built on February 22, 1957, and shipped to Amsterdam. There, for 12 days between February 28 to March 10, the two newest Triumphs were displayed at the RAI Motorcycle Exhibition. After the show, H1 was sold and registered for the road on April 5, 1957. The new Twenty-One was the way of the future for Triumph, as the company then updated its 500cc range in 1959 to unit-construction, followed in 1963 by its 650cc lineup.

History of the Triumph Twenty-One

In 1957, the Triumph Engineering Company was celebrating its 21st anniversary. The firm, purchased in 1936 by Jack Sangster, took the opportunity to dub its newest model the Twenty-One — rather conveniently, that was also the displacement of the engine — 21-cubic inches, or more commonly, 348ccs. This mid-capacity engine size was nothing new for Triumph. In the early to mid-1930s, the company produced a line of 350cc single-cylinder models, including the side valve 3/1 and two overhead valve mounts, the 3/2 and 3/5.

These machines had been designed by Valentine Page in the early 1930s. When Sangster bought Triumph, he put Edward Turner at the helm of the design department. Turner gave the Page-designed OHV singles in 250cc, 350cc and 500cc sizes a sporting flair with a dash of chrome, new paint schemes and high pipes. These became the Tiger 70, Tiger 80 and Tiger 90, respectively. Then, for the 1938 model year, he launched the seminal 5T Speed Twin. This 500cc parallel twin engine essentially dropped straight into the Tiger 90’s running gear, and painted Amaranth Red, the model helped chart a new course for the entire British motorcycle industry.

After the 5T, Turner drafted a 350cc parallel-twin machine that was set to launch in 1939 but was not released due to the war. Post-war, the 350 twin became available in 1946 as the 3T De Luxe. The touring 350 looked very similar to the Speed Twin but differed in various design elements, as the frame was physically smaller and so too were the fenders. The 350cc engine shared no common elements with the larger 500 twin. The head was cast with integral rocker boxes and the crank was pressed together, and the crankcase was smaller. Shared between the 350 and the 500, though, were the telescopic front fork and front and rear wheels.

While selling well in some markets, the 350cc 3T was always overshadowed by the 500s. The machine was not built in significant numbers and ceased production for 1951. That was two years after Triumph began selling the popular 650cc Thunderbird, and all these larger-capacity machines featured non-unit engine and gearbox construction, meaning the crankcase and the transmission were two separate castings.

It was Triumph’s small-capacity T15 Terrier (150cc) of 1953 and then its T20 Tiger Cub (199cc) in 1954 in which Turner adopted unit construction. These small-bore single-cylinder machines were built with an integral 4-speed transmission, and it was an idea Turner continued to refine by the mid-1950s when he felt there was still a hole to be filled in the mid-capacity marketplace. This led directly to the 350cc 3TA — A for ‘unit’ — and its unit engine architecture set a new course for the manufacturer when it was released for 1957, and thus began the now commonly used “unit” / “pre-unit” terminology.

A 1957 foldout brochure for the model explains, “This is the Triumph ‘Twenty-One,’ a sleek new 350 twin — new from end to end. As modern as the day, yet designed with all that skill, beauty and exciting performance that is so traditionally Triumph — performance which combines turbine-like smoothness with quite exceptional mechanical silence.”

Triumph copywriters, continued, “Twenty-one years ago the present Triumph management took over the old Triumph Company with all its fine traditions. The Triumph Engineering Company Limited came into being and in a short time produced the ‘Speed Twin,’ a motorcycle that revolutionized design throughout the world. Other famous Triumph Twins followed, built around the same engineering theme — the Tiger 100, Thunderbird, Trophy, Tiger 110. Now comes the ‘Twenty-One,’ logical descendant of them all, designed from this unrivaled wealth of experience, to give modern motorcyclists a truly modern motorcycle.”

“Modern” meant the under-square 58.25mm by 65.5mm bore and stroke parallel-twin engine was now built in unit-construction, with the 4-speed transmission housed in a cavity cast integrally with the right side crankcase. Inside the case, an intake camshaft rode up high and behind the crank, while the exhaust cam rode up high and in front of the crank. Connecting rods were steel with plain big end bearings topped with aluminum alloy pistons with a 7.5:1 compression ratio. The cylinders, although cast iron, were painted silver to mimic aluminum, while the cylinder head with its pushrod-operated overhead valve gear was alloy.

Power pulses were taken from the crank via a duplex primary chain to the clutch basket. Also mounted to the left, or drive side of the crank, was an alternator that provided power for both ignition and lighting. The distributor, mounted directly behind the right side of the cylinder, delivered energy to the spark plugs. Gasoline and air mixed in an Amal 375 Monobloc carburetor. The air filter for the intake was in the nose of a stylish new rear enclosure.

Here’s how Triumph described the pressed steel unit in its 1957 brochure, “This very attractive rear enclosure on the Triumph ‘Twenty-One’ sets a new standard of cleanliness which will be appreciated by riders and passengers alike. Of striking appearance, it is a beautifully shaped pressing, completely smooth and easy to clean.” The enclosure was soon dubbed a “bathtub” and in the all-important American market, it did not find favor. Under the dual saddle in the top of the ‘tub was a molded rubber container containing a very complete toolkit. Also under the saddle was access to the remote oil tank, and all other electrical components.

Triumph employed a cradle frame with a single front downtube and swingarm rear suspension. Perhaps imbuing the Twenty-One with some European scooter esthetics, Triumph opted to run smaller 17-inch wheels front and rear. Up front, a new full-width hub with a 7-inch brake was carried between the legs of a hydraulic fork topped with Triumph’s characteristic nacelle. Continuing to keep a rider and passenger neat and clean was the large pressed-steel front fender. Finished in “polychromatic silver grey” the first 3TAs had a smooth-topped gas tank with no center seam and no parcel rack.

After the first two Twenty-Ones, H1 and H2 rolled off the Meriden line early in 1957 and went to Holland for display at the RAI Motorcycle Exposition, the model should have launched in the U.S. shortly after. However, there was some delay in shipping and the Twenty-One didn’t appear in American catalogs until 1958. It was described in the West Coast Johnson Motors’ brochure for ’58 like this, “Here’s the newest addition to the family of Triumphs. Has a wonderful new Triumph engine of 21 cu. in. 350cc. Representing over 50 years of design leadership by Triumph. Completely new, the streamlined Twenty-One, years ahead in design.” It was now in Azure Blue as opposed to the silver-gray finish.

Now in Bill’s hands

After the 500s gained unit construction in 1959, and the 650s in 1963, Triumph continued to use essentially the same unit engine layout until the end of the Meriden run in 1983. Then, John Bloor bought the Triumph name and began the era of the Hinckley-built machines. And that’s where Bill’s neighbor, Wim Vellekoop, sent an initial query about his Twenty-One with serial number H1. Early in 2013, Wim, who’d owned the Twenty-One for many years and used it as an everyday commuter until he stored it, sent a letter to Triumph Motorcycles Ltd. “Could this Triumph 3TA/21 be a collector’s item for your factory since it is a first engine of this kind?” he wrote. He never got a response and that’s when he offered it to Bill.

“Wim was an interesting guy who’d kept all his service records and personal notes he’d made about the bike,” Bill says of his neighbor. “I bought the bike, which was very complete, but it was just an old, tired looking motorcycle. I rolled it three houses down and put it in my garage. I had a shop over there start on a restoration, and they took it all apart and that’s about as far as they got on it before I got transferred back to Houston. They crated it up and I shipped it back here.”

Over his lifetime, Bill owned three or four motorcycles but wasn’t a keen enthusiast. When Wim showed him the Triumph, he says he took an interest for two reasons. First, it was a 1957, and that was the year he was born. Second, it was a Triumph, and Bill was aware of the Triumph story. That was enough for him.

Although the bathtub was not on the bike when Bill bought it, Wim had it and included it with the sale. Lucky, that was, because finding an enclosure for a 3TA is a daunting task. With the Twenty-One in Houston, Bill had a restoration shop continue the rebuild. When he took delivery of the machine, with fresh engine and first-class paint, Bill wanted it taken to the next level. He enlisted the help of Kevin Giles, a very competent British motorcycle restoration expert who likes to maintain a very low profile. Under Kevin’s care and with his attention to detail, the Twenty-One was gone through front to back and taken to an exacting standard.

Kevin has ridden the Triumph, as has Bill’s son, but the machine has since been pickled with the fuel drained from the tank. “I thought I was going to keep the bike, but we’re in a small house and I can’t ride anymore. It’s a tough one, but I’ve decided to sell it,” Bill says.

To that end, Bill’s rare and historically significant Twenty-One will cross Mecum’s auction block at their Monterey sale, running August 15 to 17 at the Del Monte Golf Course in California. “There’s no reason to let it sit here, somebody should enjoy it, and I think it really belongs in a museum. But if somebody bought it and wanted to ride it, that’d be great, too.” MC

For the final results of the the Twenty-One’s time at Mecum Auction’s Monterey sale, be sure to check out the November/December 2024 issue of Motorcycle Classics. Contact Customer Service at (800) 880-7567 or contact us by email.