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1979 Triumph T140D Bonneville Special
Engine: 744cc air-cooled OHV vertical twin, 76mm x 82mm bore and stroke, 8.6:1 compression ratio, 47.4hp @ 6,500rpm (claimed)
Top speed: 100mph (period test)
Carburetion: Two 30mm Amal MkII
Transmission: 5-speed, chain final drive
Electrics: 12v, coil and breaker points ignition
Frame/wheelbase: Oil-in-frame dual downtube steel/55in (1,397mm)
Suspension: Telescopic fork front, dual Girling shocks w/adjustable preload rear
Brakes: 10in (254mm) disc front, 10in (254mm) disc rear
Tires: 4.1 x 19in front, 4.25 x 18in rear
Weight (dry): 400lb (182kg)
Seat height: 32in (813mm)
Fuel capacity/MPG: 4.5gal (17ltr)/30-35mpg
Price then/now: $2,700/$4,000-$10,000
In 1979, Triumph, desperate for U.S. sales, introduced the custom inspired T140D Bonneville Special. Unfortunately, it wasn't as custom or as special as Triumph's ads might have tried to suggest. Something of a failure when new, it's a rare bird today, and even old Triumph hands find themselves drawn to its unique lines.
Richard Hardmeyer was flat tracking in the glory days after World War II, when the 500cc overhead valve Brit bikes were going heads up against the flathead 750cc Harleys and Indians. He has a lot of racing stories, but this Sacramento Mile event is one of his favorite memories. "I was at the Sacramento Mile, riding a 500 Triumph twin out of Joe Sarkee's shop. I used my practice tires for the heats, but for the main event they put on a new tire. There was a film of grease or something, and when I went into the first corner I went into a slide, and slid up to the fence. Well, I held on to the bars, picked the bike up and got back into the race. In 23 laps I passed 15 national number plates and ended up in sixth place."
History of the 1979 Triumph T140D Bonneville Special
Even as the structure of the company crumbled, Triumph’s remaining stalwarts still tried to update the Bonneville. Besides layoffs at the factory in Meriden, West Midlands, there were now unfavorable exchange rates as the United States dollar weakened. Mixed with sluggish stateside sales in previous model years, the 1979 output joined a large stockpile of remaining new Triumphs. The Bonneville lineup included two models this year. The mainstay, of course, was the T140E Bonneville, introduced in ’78 with modifications that met new standards set by the Environmental Protection Agency, which decreed against escaping fuel and oil vapors.
The familiar air-cooled, overhead-valve 744cc parallel twin got a makeover with a new cylinder head. The compression ratio was reduced to 7.9:1, and output fell to 49 horsepower at 6,200 rpm. For 1979, the engine adopted Lucas Rita electronic ignition, one of the biggest steps forward before electric start was added. New Veglia instruments, Lucas switches, and a lockable seat with rear rack were added as well. But the larger development was the addition of the T140D Bonneville Special. The Yamaha XS650 Special had suggested a market niche beyond the standard roadster, and Triumph entered it. The T140D Bonneville looked exciting with seven-spoke alloy wheels and an uprated 4.25x18-inch rear tire (later 4.10x18-inch), a stepped seat, and black-and-gold livery. There was also a two-into-one exhaust with a factory-authorized sport exhaust available. The rear brake caliper was better positioned at a higher point. Priced at $3,225, the T140D Bonneville was expensive, but today’s collector finds such a detail irrelevant.
1979 Triumph T140D Bonneville Special Info