"The average rider of the late 1970s wasn’t going to
be fobbed off with an old-tech, leaky, pushrod British
twin when, for significantly less money, he could buy
an up-to-the-second Jap multi that could thrash the Bonnie
on any quarter mile length of straight. However ..."


Triumph Bonneville T140

Buyers guide


The colour scheme on this UK/Euro specification 750cc Triumph Bonneville T140 came out in 1980. Triumph (Meriden) was in trouble and was desperately trying to come up with new ways to look at an ageing bike. An electric starter appeared soon after, and the firm had ideas for a completely new machine. But the investment money wasn't there, and the hopes died a death.

IF YOU'RE LOOKING for an all-weather, all-purpose, everyday classic British bike, you’re probably staring straight at a 750cc T140 Triumph Bonneville. A lot of negative criticism has been hurled at these machines, notably citing problems with vibration and oil leaks.

But the fact remains that T140s have excellent handling, good braking, decent enough suspension, an acceptable turn of speed, and have better parts back up than just about any other classic British bike in the market place.

 As for the vibes, these never were as bad as some suggested (although a poorly set up Bonnie with an unbalanced crank is a minor torture). And the much-mentioned oil leaks are no worse than those of other British bikes. But because T140s are used more, so the leaks are seen more often. Almost nobody trailers a prized 750cc Bonnie from show to show.

Not yet, anyway.



Sump 750cc T140 Bonneville


Two of Sump's girls striking a pose on one of our T140s. It's the same Bonnie as seen on our T140 Bonneville YouTube video (see elsewhere on this page). Would love to stop and tell you more about it, but the girls are calling. Know what we mean?




History and development of the T140 Bonneville


Launched in 1973, the T140 Bonnie picked up where the 650cc T120 Bonneville left off, and the extra 100cc came with a penalty. Edward Turner, designer of the 1937 Triumph Speed Twin (the grandfather of all successive Triumph twins—and the inspiration behind a lot of other twins from rival marques) has been quoted as saying that he never intended his 500cc engine to be enlarged. Certainly to no more than 650cc.

But by the late 1960s, the Americans (in particular) were clamouring for more horses for their track and desert courses, and if Triumph couldn’t provide the 750cc upgrade, then the Yanks would.

And did.

Eventually, feeling the pressure of Japanese superbikes eating up showroom floorspace and sales, and hoping to turn US aftermarket 750cc top-end kits into much needed Triumph dollars, the company acquiesced and finally built the long-time-coming 750cc T140 Bonneville and, soon after, 750cc TR7 Tiger.


Triumph oil-in-frame chassis


These new machines were always 5-speed, and were launched with a front disc brake and drum rear and inherited the controversial oil-in-frame chassis trailblazed by the 650cc T120. That frame started out wrong, but ended up right, and has lasted around forty years without significant issues.

Styling for the T140/TR7 was a pretty much orthodox British sit-up-and-beg configuration with a build quality that the Japanese bike industry still hadn't matched. Frames were hand welded. Tanks were hand striped. The overall feel was of a value-for-money, traditional machine, albeit manufactured around a design that could have been justifiably pensioned off in the mid 1960s.

The (nominally) 750cc engine was near identical to the 650cc power unit. But the first T140s were (for production reasons) actually 724cc. Within months however, this became 744cc—which remained the cubic capacity of the Bonnies and Tigers until the bitter end.

 Development of the new seven-fifties was, by 1974, slowed by the now infamous industrial unrest at the Meriden factory in Warwickshire that saw production halted for around eighteen months—and, woe of woes, at a time when the Japanese were becoming increasingly aggressive and competitive; a fatal commercial combination that put a large number of nails in the coffin of what was left of the British motorcycle industry. Which, with Norton just about the hit the skids, was really just Triumph.


Rear disc brake and revised cylinder head


By the time the Meriden industrial situation/debacle was resolved, the Triumph Trident (which was in fact the true competition for the T140) was almost dead on its feet, leaving the ageing Bonnie desperately trying to claw back prestige and customers with a package that beginning to show a lot of mechanical wrinkles.

 The Triumph engineers, however, were not giving up without a scrap, and the 750cc Bonnie and Tiger was, if not exactly technically brought up to date, then at least patched up enough to scrape it through the increasingly stringent noise and environmental pollution laws that were almost as big a problem as the incoming Japanese—and, come to that, the incoming Germans who, with their new range of BMW Boxer twins, were rapidly shedding their “old man” image and looking increasingly attractive to a younger aspirational biking set.

 And then there was Harley Davidson knocking on the door and slowly getting its act together with a range of brutally attractive, if expensive, 1000cc and 1200cc twins.

In 1976 the T140 was finally given a rear disc brake. In 1978, the bike developed a new, parallel-port cylinder head (to replace the earlier splayed-head that had been a feature since 1959), while the TR7 Tiger, which had started with a single carb, retained it throughout).

That same year, new carbs were also introduced for the T140 (Amal Mk2s as opposed to Mk1s; the Tiger kept its Mk1), and overall, the bikes were looking more angular and modern—and a little too angular and modern for many Triumph diehards. Worse still, performance was down and vibration was up. At least, the modern generation of wannabe gonzo motorcycling journalists felt so, and said as much.

Loudly, and often.


Meriden under pressure


Unquestionably, such hostile press opinion cost Triumph some sales—but perhaps not as many as you might expect. The average rider of the late 1970s wasn’t, after all, going to be fobbed off with an old tech, leaky, pushrod British twin when, for significantly less money, he could buy an up-to-the-second Japanese multi that could thrash the Bonnie on any quarter mile length of straight.

However, on the curves it was a little different. In fact it was a lot different. At that time, Japanese bikes had notoriously bad handling, and British twins (and triples) were famed for their sure-footedness. The average Jap superbike had a huge hinge in the middle and (often) a distinct wobble when it approached anything like its theoretical top speed.

But the Japs were learning fast, and there wasn’t really any place else to go for the Bonnie; certainly not without radical revisions, for which there simply wasn’t the development cash anymore.

In 1979 the Yamaha 650 Special (twin) appeared; a devilishly handsome piece of kit that did pretty much all that the T140 and TR7 could do (except handle), and at a lower price. It was largely also oil tight, and vibrated less, and had a good electric starter. These 650cc Yams, since 1968, had built a reputation as dependable all-round machines, and they sold in huge numbers around the world.

But this particular Yam, with its cast wheels and black and gold livery, hit the right note during the right summer and had exactly the street cred required by contemporary riders looking to build or maintain a sub-hooligan wish-I could-afford-a Harley image. Whilst at the same time, the Yam Special was not so left-field that ordinary guys looking for a simple, decent, attractive everyday twin would shy away from.




Triumph T140 from Sump


▲ One of Sump's own T140s, lightly customised with Lester cast wheels, Triumph TSS side panels, a two-into-one-exhaust, a Bates headlight, wider handlebars, and bright yellow livery. We love it.




Bonnie Special T140D and electric starters


Regardless, Triumph felt the pinch and rapidly responded with the Bonnie Special (Lester cast wheels, black and gold livery, two-into-one exhaust); a machine that in terms of looks and quality of materials easily shunted aside the Yam Special. But the king of the twins was on shaky ground (not least because it was 10-15% more expensive), and knew it.

The following year, the T140/TR7 gained an electric start; the first on a British motorcycle that actually worked. For a while, anyway. There were later problems with Triumph's hurriedly engineered system, but none of which can be shown to have really hit sales (except in the second hand market). And within three years of that auspicious event, having seen relatively minor (and some not so minor) revisions, the Triumph twin was dead. That was 1983.

Part of the problem was a collapsed US market. Part of it was business export market guarantee intrigues. Part of it was that the Bonnie was simply looking less and less relevant.

And sales had truly plummeted during those last few years despite most riders bearing a grudging respect for the T140 (some of whom who were, naturally, always meaning to buy one, or at least cadge a ride on one someday). And of course the biking press, now that the dirty deed was done, said that it was a pity that the British bike industry was over. But never mind, we’ve still got the Japs ....

 It might have been kinder had someone pulled the Bonnie plug a little earlier, because at the end of production, the 1973 flood of Bonnies had turned into a pathetic trickle down the drain of history with bikes being offered in any specification and any colour, just so long as you bought something.





▲ 750cc TR7T Tiger Trail. Built between 1981 and 1982, these rare twins have a small but loyal following. Check our TR7T Tiger review.




Harris Bonnies and the end of the T140


It was a sad end for a company that really loved its product; an end that enjoyed a short-lived resurgence in 1985 when the late Les Harris bought a short-term manufacturing licence and built another 1200 or so bikes up until 1988.

Today, T140 Bonnies are as good as they ever were (whatever that means to you), with overall reliability much higher (largely thanks to retro-fitted electronic ignitions; the standard T140 never got electronic ignition until 1979.

They’ll leak a little oil, which can be ignored without issue, or (mostly) fixed if you just take the trouble to rebuild them properly. On the plus side, a little black gold splashed around a motorcycle isn’t such as bad thing if you want to keep the lethal oxides at bay.

Overall, Bonnies and TR7s are nimble, tractable, decent stoppers, and maintenance light. And when they do go wrong, they can be sorted fairly easily. Also, they return around 50-55mpg. You won’t see much change out of 100mph, but acceleration is still pretty good, even two-up.

The seat height is fairly low at around 31-inches, and only those with extra short inside leg measurements will have to worry about getting both feet flat at the same time on opposite sides of the saddle. Not that that's too important. The 750cc Bonnie is an easy machine to throw around when stationary.


Is the T140 Bonnie or TR7 Tiger the bike for you?


Most T140 Bonnie or TR7 Tiger riders wear open-faced crash helmets. But if you really must wear a full-faced lid, this is one of the few British bikes that will indulge your obsession with your bridgework without looking too ... well, naff. So much so that Triumph was keen to use full-faced helmets in its later adverts (see main image) as if to prove to the world that what was pretty long in the tooth was actually very modern and cutting edge.

But which bike should you buy? The short answer is whichever one you most enjoy looking at—provided the price is in line with current market expectations. None of T140s have particular "issues", except perhaps the electric start models (which need a little extra care with the starter gear sprag clutch), and the T140W TSS derivation (with its eight-valve head and other under-developed revisions). If you're considering an early bike (pre-1976), you're strongly advised to think in terms of left or right side gear change.

It can make a major difference to some riders.

If you want to cut your maintenance chores a little further, and without a significant power penalty, buy a TR7 Tiger.

After a long time in the low value, low status doldrums, 750cc oil-in-frame Bonnies and Tigers are now steadily rising in value and prestige. And rightly so. For commuting, these bikes can easily take the daily rough and tumble, being nimble in traffic with enough presence to command some respect on the road. For touring, they're long legged enough to carry you for hundreds of miles a day, two up and with luggage, without blowing their cool and leaving you exhausted. And for Sunday fun and games on your favourite back roads, a T140 will do everything demanded of it by the average classic biker, with plenty in reserve.

They can be tuned and beefed up to show a genuine 115-120mph on the clock. But you'll also have to drop the bars and shift the footrests back to do it. The compression will need to be raised; bigger carbs will need to be fitted; and expect to do a lot of headwork (porting, polishing, and perhaps lighter valve springs).

Meanwhile, stripping some of the excess tin can cut the flab by around 60lbs, or more, thereby liberating a few extra bhp.

 And if anyone tells you that the oil-in-frame T140s are rubbish, just fix up a time and a place and let us know. We’ll send some of the boys round to sort it out.


Triumph T140 Bonneville ownership tips


1. Use a quality 20W50 low detergent multigrade oil and change every 1500 miles maximum, or less.


2. Chrome discs make for worse braking. De-chrome, or replace. Un-chromed cast iron discs are superior.


3. Check the wiring looms carefully when buying. Many looms haven't been replaced in over 30 years.


4. Use the best fuel you can get, and avoid cheap supermarket petrol.


5. Rejuvenate the braking system by replacing old hoses. And change the hydraulic fluid at least every two years, or less. DOT 4 will do nicely.


6. Rough fork action can often be fixed by loosening the forks from the spindle upward (including yokes), and retightening in the correct sequence according to the factory workshop manual.


7. Check regularly that the oil is returning. Raise the seat, unscrew the oil filler cap, and run the engine. There's a small pipe just visible at the top
of the frame elbow. Oil should squirt from that pipe in "glugs". You won't see a continuous stream. Get to know the feel of new and old oil.


8. Check the centre stand for smooth action and looseness, and check the side stand for sloppiness.


9. Gears should change cleanly and click into place. You might get a first gear clonk. But beyond that, the gear changes should be fairly slick.


10. Clutches are fairly heavy, but should bite smoothly and progressively.

Keep a spare cable with you—or, at least, an emergency cable repair kit.

Back to the top


Sump: 2010

Updated: 2013




Triumph T140 Bonneville 750

T140 Bonneville Specifications
Triumph T140 & TR7 models and variants
Top Triumph T140 specialists & links
History and development of the T140 Bonneville
Triumph oil-in-frame chassis
Rear disc brake and revised cylinder head
Meriden under pressure
Bonnie Special T140D and electric starters
Harris Bonnies and the end of the T140
Is the T140 Bonnie/TR7 Tiger the bike for you?
Triumph T140 Bonneville ownership tips

Triumph Bonneville T140 quick review

Triumph Bonneville T120 quick review

T120/T140 Bonnie owner?


We've just updated our Triumph Bonneville T140 buyers guide, and we're looking to add to it with more Bonnie tales and images from Bonneville owners. We run three of these bikes, but we just can't get enough of them. So show us yours and we'll show you ours. All T120s and T140 variants are welcome. We're talking about TR7 Tigers, TR65 Thunderbirds, TSXs (we've got one of those too), TSSs or what have you. Images need to be large-ish, and we'd like to see what you look like. Interested?



Triumph Bonneville T140 and Tiger TR7 prices

People are asking an awful lot of money for T140s these days (late-2013), and we're pretty sure that expectations are considerable higher that real world prices

We've been recently looking at Jubilee Bonnies and Royal Wedding Bonnies that are asking up to £13,000. Meanwhile, other sellers are struggling to part company with very clean, low mileage T140s at £5,000.

That represents a £7,000 - £8,000 differential, and the fact is that Jubilees and Royal Weddings just aren't that desirable anymore (especially so for the Jubilees).

Generally speaking, you can buy a decent privately owned UK or US specification T140 Bonneville, taxed and tested for the UK market, at around £4,000—or even £3,250 - £3,500 if you're patient and haggle.

Meanwhile, prices for Triumph T140D Bonnevile Specials appears to have slowed a little. There's no obvious reason for that, except the general state of the economy. We've seen quite a few at sub-£4000 whereas we would have expected to see them fetching a little higher when compared to standard T140 prices. That said, many of these "Specials" are not originals, and they (naturally) need to be unmolested and 100 percent "correct" to draw in the collectors.

TSS Bonnies (8-valve heads) are too rare to be certain of prices, but £6,000 - £7,000 has been recently asked. We're doubtful that anyone is getting that at present. And although these (fast) machines can be made to run well, many owners still haven't really got to grips with their foibles, and that helps hold down prices.

Elsewhere, Triumph Tiger TR7s currently fetch about the same prices as T140s. If anything, many riders these days are opting for the single-carbed Tigers in preference to the twin-carbed Bonnies. A decade ago, TR7s generally fetched slightly less.

The 750cc TIger Trail (TR7T) is also too rare to give accurate prices, but you can generally figure to pay about the same as you would for a TSS—which is undeserved really because the difference between the TR7T and the standard T140 isn't that great, and standard T140s are certainly better for all round road use.

The ultra-rare short-stroke 650cc TR6T Tiger Trail carries a slightly higher premium than the TR7T at up to £8,000 for a reasonable one, and maybe £5,000 -£6,000 for a poor example.

The 650cc TR65 Thunderbird (1981-83) now sells for roughly the same price as a decent T140 at £4,000 or so, but sellers often expect a lot more (£5,000 - £7,000).

Lastly, the 750cc TSX is currently fetching fairly big numbers, so expect to pay £7,000 - £8,000 for a very clean and original example—and these prices, we feel, could jump significantly higher once the economy picks up. There's good investment potential there.

1973 Triumph TR7 Tiger


1973 750cc Triumph Tiger.

Single carburettor. Disc front brake, drum rear. Simple. Tried. Tested. Great for touring. Later T140s/TR7s would suffer emissions restrictions, but any T140 can be "dirtied" up with a few engine mods. You'll instantly feel the improvement in performance.

1979 Triumph T140E Bonneville


1979 Candy Apple Red T140 Bonneville.

Disc brakes front and rear. Gaiter-less forks. Well built. Reliable. And oil tight.

1979 Triumph T140 Bonneville Specifications


Type: Air-cooled, OHV, twin

Capacity: 744cc (750cc)

Bore & Stroke: 76mm x 82mm

BHP: 44 @ 7000rpm (variously quoted
at 46-50bhp)

Compression ratio: 7.9:1

Transmission: 5-speed, multi-plate
wet clutch

Brakes: 10-inch discs front and rear

Electrics: 12-volt, electronic ignition

Front suspension: Telescopic,
two-way damped

Rear suspension: Swinging arm with

Girling shock absorbers/dampers

Wheels: 4.00 x 19-inch front,
4.25 x 18-inch rear

Weight: 410lbs (dry)

Maximum speed: 105mph

Meriden Triumph T140 - primary side.


Triumph T140 & Triumph TR7 models and variants

T140V Bonneville 750cc

T140E Bonneville 750cc
TR7 Tiger 750cc
T140J Jubilee Bonneville 750cc
T140D Bonneville Special 750cc
T140E Bonneville Electro 750cc
T140ES Bonneville (Electric Start ) 750cc
TR65 Thunderbird 650cc
T140ES Bonneville Executive 750cc
TR7T Tiger Trail 750cc
TR65T Tiger Trail 650cc
T140AV Bonneville (Anti Vibration)

(Police model) 750cc
T140W TSS 750cc
T140LE Royal Wedding Bonneville 750cc
TSX 750cc Harris Bonneville 750cc

750cc Triumph T140 Bonneville engine cutaway

The unit 750cc T140 engine as

drawn by the late Lawrie Watts.

Triumph's 8-valve T140W TSS

Triumph's 8-valve T140W TSS.
Fast but flawed. But fixable.

1978 Triumph T140V Bonneville


▲ But what do T140 Bonnie
and TR7 Tiger owners say about their bikes?

Click on the image above to find out

Triumph T140 Bonneville book from Sump


Click the image above for details of Sump's essential T140 Bonneville/TR7 Tiger  buyers guide available NOW!
Or press the GREEN button below to download an eBook showing sample pages.
Tip: Right click with your mouse to control the various eBook functions. Click the pages left or right to turn forward or backwards, respectively.


Triumph Bonneville movie on YouTube


Want to see a Triumph T140 Bonneville on the move?

Click the link below and take a ride.


Top Triumph T140 Bonneville specialists & links


Norman Hyde



Triumph Owners Motor Cycle Club

Got the bike? Join the club. Branches nationwide. Knowledgeable people. Big social calendar.



Grin Triumph

Telephone 0776-555-3258 (Urgent enquiries only, please)



T8 Motorcycles

Telephone 01394 279929



British Cycle Supply Company

US and Canada based suppliers of Triumph, BSA and Norton spares. Lots of interesting stuff. These guys ride with pride.



MAP Cycle

US based British bike parts. Huge range of high quality, high performance precision spares for BSA, Triumph and Norton. Original equipment and custom parts.







All this and the open road


Copyright Sump Publishing 2014