Triumph T140W TSS

It was back in March 1982 when the ill-fated £2,399 750cc T140W TSS hit the streets. The Meriden Worker’s Co-operative—then just a year away from irrevocable meltdown—had only one meal on the menu; the T140 Bonneville, albeit served up on a variety of crockery designed to appeal to a range of palates.

The TSS was the chef’s special; a revised T140 with the usual meat and potatoes, but with a dash of extra sauce, resulting in a (theoretically) smoother, faster, more efficient air-cooled parallel twin with 120mph on tap and looks that could only come from a British motorcycle engineering works. Triumph claimed a 20% power hike.

But if the operation was a success, the patient died—not because the concept itself was flawed, but simply because there wasn’t sufficient aftercare to refine, develop and debug an otherwise proven engineering solution. In short, Triumph hit the skids before the bike could mature, and that was that.

Ricardo Engineers and Weslake Engineering

The TSS, however, wasn’t Triumph’s first flirtation with a four-valve-per-cylinder concept. Way back in 1921, Sir Harry Ricardo (1885-1974) of Ricardo Consulting Engineers Ltd took an otherwise stock 500cc Triumph single and machined a new barrel, head and piston and turned a plodder into a TT rodder. Triumph (Engineering Ltd), then based at Priory Street, Coventry, was said to be impressed with the performance but not with the additional production costs, so the idea was canned.

Until, that is, Weslake Engineering came along in the late 60s and proved their own brand of bolt-on four-valve-per-cylinder head for 650 and 750 Triumph twins. It took over a decade before Triumph capitalised on Weslake’s—ahem, enginuity—and after some hasty last chance revisions, the TSS was born.

▲ Triumph TSS, primary side. The crank was reworked with bigger journals to increase the stiffness. It was said to rev to 10,000rpm. Those large side panels were designed to cover the German made Bing CV carburettors demanded by the US market. British TSS's ran Amals.

Engine and performance

Based around a stock T140 Bonneville chassis, the TSS used T140 engine cases, timing gear, clutch, and gearbox. The crank, however, was all new; a one-piece forging with larger diameter (but narrower) journals at 1.875 inches and all-over machining for improved efficiency and balancing. Interestingly, the cylinder bores of the TSS were spaced approximately ½-inch further apart with correspondingly revised big ends and small ends. Consequently, a TSS crank will fit only another TSS.

The 9.5:1 compression barrels were all-alloy and capped with a one-piece cylinder head/rocker box arrangement located (in Evo Sportster fashion) by through-bolts as opposed to head bolts and barrel base studs.
Pistons were flat-topped with valve cutaways. Spark plugs (12mm) were centrally located in hemispherical combustion chambers.

In 1982, Classic Bike’s Mike Nicks test rode the TSS and reported,

‘ … more important to customers seeking a practical sports machine for all-year usage on the road is the engine’s four-valve flexibility, which enables the TSS to accelerate dynamically from 40mph, just 2,500rpm, in top. This feature alone makes the TSS a delight to ride—you don’t have to change down to negotiate knots of traffic, medium-radius roundabouts, or country lanes.’

Meanwhile, other contemporary road tests broadly agreed that the TSS was everything the T140 was, sans vibration and with improved power throughout the rev-range. Which resulted in a relatively lightweight 750cc five-speed parallel-twin, with electric start, dependable brakes, excellent handling—and a redline shifted from 7000rpm to (theoretically) a whopping 10,000.

The footrests, however, as with all Bonnies, are too far forward. And the clutch could be lighter. But the gears are slick and quick once you get into the rhythm (although early gearboxes were criticised for being “notchy” until well worn in). The triple Lockheed disc brakes, meanwhile, stop the action with confidence, if not cockiness.

But the suspension, like all T140 suspension, is never more than adequate. Early demo models were ill-prepared, and production bikes were plagued with troubles that gave the machine a reputation as one to be avoided. They can be sorted, but you have to persevere. And when they do go, they really go. But bad luck, because most of them are gone—with many broken for spares or (sin of sins) converted to stock T140s.

All said and done, you really need to be something of a home-engineer or mechanic to live with a TSS. Alternately, a good top-end overhaul by a T140 racing specialist would almost certainly set one to rights.

At a price.

Conclusion? This is a collector-magnet that, paradoxically, both attracts and repels, and buyers will always beware unless convinced that the one they’re looking at is properly sorted
 

▲ Triumph TSX-8. This "factory custom" should not be confused with a TSS, but the TSX-8 shares the top end and promised considerably improved performance from an "ageing" engine design. Only one or two of these electric start cruisers were manufactured by Meriden Triumph (note the absence of a kickstarter). Features include Morris cast wheels front and rear (19-inch and 16-inch), and shorty (big bore) megaphones.

Triumph TSS History 1982-1983

1982: Introduction of the 4-valve-per-cylinder TSS, developed from the 2-valve-per-cylinder T140 Bonneville. Details include rubber-mounted rider footrests, Veglia speedometer and rev-counter, electric- and kick-starting, stainless steel mudguards, simplified grab rail (removal of parcel rack), Paoli plastic fuel taps, Marzocchi Strada shock absorbers, extended side panels, larger tool kit, repositioned centre stand and silencers, optional Morris cast wheels (at £100 a pair). Production was said to number forty bikes per week.

1983: No significant revisions. New model proposed with anti-vibration frame as standard, rear-sets and revised seat, but discontinued this year. A total of 438 bikes were said to have been made, most of which went to the USA.
 

▲ Triumph T140W TSS for 1983. In June 2015, this very original looking 8-valver was sold by Historics at Brooklands for £8,960. The auction listing tells us: "It is in amazingly good original condition and benefits from a new crank, crank cases, barrels and a new head." If that's true, what does this suggest to us about a bike with only 10,720 miles on the clock? Questions.

Keeping a Triumph T140W TSS on the road

“I’ve got a TSS and spent a lot of time and money fixing it. I used Nourish Omega pistons (forged) with a 3 thou clearance—which is right for a road bike. I had the head skimmed 25 thou to get a better seal on the cooper rings, and to compensate for the raised compression I fitted a wee alloy plate under the barrels (1.5mm). Also, I used modified Nourish alloy tappet blocks, instead of the standard cast-iron blocks, and Nourish alloy push rods. The alloy maintains the expansion rate of the top end, which keeps the gas and the oil in. I replacement the rocker spindles with Nourish rocker spindles. They were a straight fit. The crank was reground and fitted with car-type shells. The cylinder head wasn’t porous. Now the bike runs well, but it took some time and a lot of effort getting there.”
- Grin, Grin Triumph

“General cycle parts for the TSS are not a problem. But barrels, con rods, pistons and cylinder heads are out of the questions—although we have valves in stock. I have ridden a TSS, but not at very high speed. My impression was that they’re decent enough bikes, but for my money, the stock T140 is perfectly good.
- Tony Cooper, TMS

“The TSS was a classic cost-cutting exercise that delivered a poorer product. In about 78/79 we built the 8-valve kit for Triumph. From that they made the TSS. For cosmetic reasons, Triumph altered the shape of the cylinder head casting and made some other minor changes. However, they didn’t use the same cooper ring recess depth as ourselves, which were 30 thou deeper on their head. That resulted in poorer cylinder sealing. And different batches of heads were no doubt machined differently with varying results. There was also porosity problems with some batches, and on other bikes the valve seats worked loose and valve springs broke. We can make engine spares for the TSS, or can supply our own bolt-on T140 8-eight valve kits for £1600—which is everything from the barrels upwards, except the carburettors.
- Dave Nourish, Nourish Racing

“When TSS’s are sorted they go very well. But in many ways they were a retrograde step. As I understand it, Triumph took the Weslake cylinder head specification and remachined it closer to the earlier Rickman spec, which wasn’t as well developed. I did once put an aftermarket 8-valve top end on a pre-unit 750 Nourish Racing bottom end. It went very, very well throughout the rev range. Regarding spares, we can supply pretty much all the running gear. But items unique to the TSS—such as side panels, cod rods, pistons and cranks—are very hard, if not impossible, to get and will have to be made.”
- Robert Knox, T8 Triumph Spares

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