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.