Motorcycles On-Line
Triumph Bonnie
Oh dear, oh dear. I'm very, very sorry, and all that, but what on earth are Triumph doing? Yes, I know it's a nice nostalgia trip and from certain angles looks just like that 1969 machine of your dreams. And, yes, I know it's a modern vertical twin, nicely refined to remove all those little horrors of sixties engineering that could add up to serious highway mishap. And, yes (again), I know that compared to an entry level Sportster it's lithe, well braked and even spirited. But?
Well, come on, this is the year 2001, a new big twin should weigh in at around 350lbs (just like a sixties Bonnie) or even 300lbs if the engineers were to apply the same kind of effort that the Big Four put into their hyperbikes. I understand how the Japanese made their seventies big twins work (XS650, Z750, GR650), how they resulted in being heavy where the old Brit's were light and lithe, but those constraints go out of the window when you apply modern engineering techniques and materials.
The point about vertical twins has always been their relative narrowness, allowing them to be mounted low in the chassis with resultant superior stability and, when allied with low mass from such a simple design, ease of flickability. Modern fours have been pared down to a miraculous lack of mass but still suffer from wide engines, highly mounted in the frame. They get away with such silliness on the back of strong chassis and high tech modern tyres - the riders pay the price in trips to the tyre shop every 2000-4000 miles.
The Japanese have either used excessive chassis mass to absorb the vibration from simple vertical twin engines or have added counterbalancers which, again, added mass to the design. The result was usually some dire handling or a general feel of malaise. The nearest the Japs have some to big vertical twin nirvana, the TDM850, the decade old machine a mere ten pounds lighter than the Triumph Bonnie but at least having an extra 15 horses, despite the added complexity of watercooling. Early Yamaha XS-2's, back in the seventies, made 54 horses, weighed less than the Triumph and only had 650cc to play with. So sorry, I can't find any aspect of the new Triumph's engine that is in the least bit impressive.
The cheapest Sportster costs $6000 but by the time you've added some bits and bobs to that stripped down machine, more likely you'll have spent around the seven grand that Triumph demands for its new Bonnie... so at least call it competitively priced. Those 883's weigh in at a tad under 500lbs, run out of puff at 90mph and handling finesse at 75mph... so Triumph beats it on all the basics despite its deplorable excess of mass for a British vertical twin.
True, the Triumph only really shows its heaviness at low speeds and when trying to park it in awkward gaps, but hardly any worse than any other 400 plus pound machine. Stability in corners, at speed, is fine, way ahead of sixties Bonnies, with none of that machine's tendency towards a back end waltz... no doubt, equip the old bugger with modern tyres and disc brakes it would feel like the frame's breaking up under the new cornering and braking forces. Given three decades of motorcycle development it would be odd if things were otherwise.
The frame is the usual period piece, majoring in excess tubing... it's surprising that Triumph didn't use their original spine frame (from the triples and fours), but then perhaps not as the period look would've been lost. Don't know if they intend to use the engine in some other models, it probably has a bit of tuning potential.
A few detail lines on the engine cases don't look quite right, down to their existence as styling themes rather than emanating from mere functionality but overall it's not a bad rendition of retro style. The engine is a thoroughly mad piece of design - the four valves per cylinder demanding an oil cooler; an otherwise absurdity on an engine that only makes 60 horses from 790cc. For that kind of power, a two-valve design with a single carb more than sufficient - less expense, less maintenance and less mass.
Again, absurdly, the pistons move up and down together, requiring a hefty amount of counterbalancing to get rid of the resultant huge quantity of primary vibration. Honda sussed this in 1965, with their 180 degree crank CB450, and Suzuki more or less perfected the design in the GR650 Tempter. Having the pistons moving up and down together is a part of the British engineering tradition, but only because it was the only way they could manufacture engines; having their gestation and inspiration in single cylinder designs, circa 1936. Modern engineering has no such constraints.
The combination of silly engineering (for a 60hp engine) and excessive mass adds up to typically preposterous frugality - any sane person would expect 60-80mpg but it came as no surprise to me that the reality was 35-50mpg, 45mpg being a typical result from what passed for spirited riding.
Top gear rolls-ons were not particularly impressive, though power delivery was linear without any hiccups. 60-100mph cruising and total apathy on the gearbox you could just about get away with, but the bike was rather more spirited in the fourth of its five gears. Top speed was an indicated 115mph, when it has to be said that only the most biased of owners would complement the engine on the level of vibes it gave out, although most of the time it was as smooth as the much more powerful TDM850. Torque wasn't on a scale that would impress 883 Sportster owners' but made for generally easy riding.
On the other hand... the mixture of born-againers, deathtrap cruiser victims and nostalgia fans whom the Triumph is aimed at, will find little to complain about. Indeed, it seems ideally suited to a world littered with speed traps and PC idiots; the dynamics of the machine well ahead of smaller Harleys, Japanese imitators and miscellaneous customs - you can sort of have your cake and eat it.
A modern classic it isn't. If you want a 650 twin with lots of class, modern engineering and an excess of fun, albeit one suffering a similar lack of outright power to the Bonnie, then buy a Suzuki SV650!
Mark Thompson
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