1983 Triumph Bonneville TSS

1983 Triumph Bonneville TSS Background & History

The 1983 Triumph Bonneville TSS was introduced at a time when Triumph was on to the brink of extinction.  Still, the optimists at the Meriden Co-Operative (the worker-owned Co-Op that had owned the Triumph brand since 1975) still believed it could be turned around. And the only way was through product. Nothing like an entirely new DOHC 4-cylinder or the like, but maybe a whole new 4-valve (per cylinder) head for the antiquated 1983 Triumph Bonneville was within reach. As strange as this sounds today, literally weeks from closing their doors, it probably made sense at the beginning of 1983.

ABOVE & BELOW: The 1983 Triumph Bonneville TSS was a handsome machine, and fast (for a Triumph), but would it be enough to save the company?

Struggles at the Meriden Co-Op

What the public didn’t see was the life-or-death, day-to-day struggles the workers and management of the Co-op were going through just trying to survive. There always seemed to be a salvation of some sort within reach, however, either through public or private funding. Undercapitalized such that they couldn’t even afford to produce the 1983 Triumph Bonnevilles that had been ordered by dealers, they were told by all the “experts” that funding would only be possible with a solid 5-year plan to turn things around. And new products were at the top of the list. On a shoestring, the resourceful boys at Triumph managed to cobble together the next-generation of Triumph motorcycles, the Diana 900cc DOHC water-cooled twin that stole the NEC Motorcycle Show in 1983 in England. Alas, the money wasn’t there, and this potentially successful machine never reached production.

The compact all-alloy top end of the 1983 Triumph Bonneville TSS contained 4 valves per cylinder and the forked rocker arms to actuate them.  Note the electric starter drive on the timing cover.  All TSS's were electric start.

Triumph needed to do something, and in this, their last year in business, they really pulled out the stops. Considering how strapped for cash they were and how little they had to work with in terms of modern equipment and manpower (over 2/3 of the Meriden workforce had been laid off by this time), doing a radical redesign of the Bonneville’s entire top end and major parts of the bottom end was a daunting and ambitious undertaking. But again, those scrappy Brits at Meriden found a way.

1983 Triumph Bonneville TSS Design

The TSS was essentially a standard 1983 Triumph Bonneville T140ES (ES = Electric Start) with the addition of an entirely alloy cylinder and head which was based on the old Westlake 8-valve racing heads of the 1960s.  Westlake offered technical help and licensed Triumph to produce them. The engine cases were standard T140ES, with an all new crank turning on higher-spec bearings, supposedly able to spin to 10,000 rpm. This one-piece steel forging had larger diameter 1.875″ big-end journals and thicker webs. Interestingly, the bore centers were spread apart by 1/2-inch, so offset connecting rods were used to make up the difference. This was done to make room for the complex rocker arm system, and to improve cylinder cooling.  The top end cooling fins were of a higher pitch than traditional Bonnevilles, and more square. Compression ratio was 9.5:1 and the conventional head gasket was replaced with 2 squish-rings that seated in a machined groove around the combustion chambers. There were still 10 head bolts, but the outer 4 were now studs running all the way through the cylinder block to the crankcase. The 4 valves per cylinder were now more steeply angled toward the vertical than before. The valves in a traditional Triumph 650/750 twin are at a 90-degree angle relative to each other; the TSS valves were at 60 degrees, which allows for better flow and were actuated by forked rocker arms, each operating two valves apiece. The head was cast such that the rocker shafts no longer rode in detachable rocker boxes, instead they were supported by beefy bosses cast right into the head.

This is an improvement that would have benefited the traditional Triumph Bonneville engine greatly, since the detachable rocker boxes are under such rocking forces, which led to some deflection in the rocker shafts.  This also contributed to oil leaks around the rocker boxes.  But not on the new TSS.  Instead of rocker boxes, they were actually rocker covers because they were no longer providing structural support for the rocker arm shafts. The entire top cover could be removed on the TSS revealing the valve gear and making it much easier to adjust the valve clearances on those eight valves.

Teething Problems with the 1983 Triumph Bonneville TSS

The 1983 Triumph Bonneville TSS was probably a good design, all things considered, but unfortunately quality control issues plagued it from the start. Porous head castings were a problem. Early heads were produced by Westlake, who couldn’t seem to deliver high quality heads that didn’t leak oil.  So, Triumph took over production in-house, under license from Westlake, and began producing TSS heads for themselves, solving the porosity problems.  The TSS used 34mm Amal Concentric MkII carbs in England, but the US had to do with the same old 32mm Bing CV carbs, because of emissions regs.

1983 Triumph Bonneville TSS Running Gear

The 1983 Triumph Bonneville TSS got a Brembo rear master cylinder, while everything else in the braking system was sourced from Lockheed in America, including it’s twin front discs and single disc out back.  Italian Marzocchi shocks were used on all 1983 models, with the TSS using Marzocchi’s top line Strada units with remote oil reservoirs. The TSS got matte-black fork sliders. Optional US-made Morris alloy wheels were now fitted to every 1983 Triumph Bonneville with the exception of US-market T140s, which retained the wire wheels.  All US-bound TSS could be ordered either way. The 1983 Triumph Bonneville TSS could be painted all black with gold double pinstripes, or black with red flashes.

All of the goodness stuffed into the engine of the TSS made 58 horsepower at 6500 rpm to the standard Bonneville's 49 hp.  A big improvement, but not enough to challenge Honda.  What was also not enough was production.  The Meriden factory couldn't produce enough standard 1983 Triumph Bonnevilles' to meet dealer orders, and these weren't big numbers.  Triumph was broke, had laid off two-thirds of its workers, and couldn't afford to pay suppliers for the parts they needed to build the bikes.  It was a vicious cycle and it was quickly winding down.  For all the money and effort that must have gone into the development of the 1983 Triumph Bonneville TSS, money they couldn't afford, they only built 438 of them, of which 112 were exported to the US.  Even if the TSS had been all it was hoped, the minuscule volumes at which they were produced would never have saved the company.  On August 26, 1983 the Meriden Co-Op produced it's last motorcycle, then shut off the lights.

ABOVE & BELOW: The triple disc brake systems were supplied by Lockeed, and were standard Bonneville fare without the chrome caliper cover.  Note that the discs were not cross-drilled from the factory, this was done aftermarket.

The End of the Line

In the end, one must wonder if they knew how close to the end it were, otherwise why come out with a radical new bike? They must have made themselves believe that the TSS would do the trick, get them back into the game. In the end, hot rodding a 40-year-old pushrod twin would have never worked in the face of technologically-advanced new 3-, 4- and even 6-cylinder bikes pouring out of Japan. The same year Triumph introduced its quirky TSS, Honda came out with its 750 Interceptor with state-of-the-art water-cooled DOHC, 16-valve 90-degree V-4 engine set in a true racing frame, that was fast, smooth, sexy and well put together. The Interceptor ushered in a whole new age of race-inspired sportbikes that would certainly have woefully outclassed the ancient 1983 Triumph Bonneville, no matter how it was modified. Times had changed, progressed moved on. The Triumph Bonneville, once the fastest production motorcycle in the world, was now an outdated, irrelevant relic of the past.

1983 Triumph Bonneville TSS Specifications

---

1983 Triumph Bonneville TSS Books

---

---

---

---

---

---

---

---

More Triumph Bonneville Pages

1959 T120 Bonneville

1960 T120 Bonneville

1961 T120 Bonneville

1962 T120 Bonneville

1963 T120 Bonneville

1964 T120 Bonneville

1965 T120 Bonneville

1966 T120 Bonneville

1967 T120 Bonneville

1968 T120 Bonneville

1969 T120 Bonneville

1970 T120 Bonneville

1971 T120 Bonneville

1972 T120 Bonneville

1973 T140 Bonneville

1974 T140 Bonneville

1975 T140 Bonneville

1976 T140 Bonneville

1977 T140 Bonneville

1977 T140J Silver Jubilee

1978 T140 Bonneville

1979 T140 Bonneville

1980 T140 Bonneville

1981 T140 Bonneville

1982 T140 Bonneville

1983 T140 Bonneville

Hope you're enjoying my website.  Glad you're here, take some time to look around.  I'm just getting started though, with lots of great content, pictures and specs on literally hundreds of classic British motorcycles left to go.  It is my goal to cover every year of every make, and every model of British bike.  You can join me in my quest.  If you have a classic Brit bike, take and/or send me some great photos of it along with a description.  Email coming soon.  More pages coming soon.  Please be patient, and hold on to your hat.  Thank you for visiting ClassicBritishMotorcycles.net.

Copyright 2024 by ClassicBritishMotorcycles.net.  All rights reserved.

---

---

Whitworth Tools for sale

---

---

2025 Classic Motorcycle Calendars are here!

---

---