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Kawasaki Z 750 B, Triumph Bonneville 750 and Yamaha XS 650

Comparison of parallel twins

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Parallel twins have a long tradition. In England. Can the Japanese "Copies" from the 1970s to keep up? A comparison drive should bring clarity: Start your engines, please.

W.he consciously chooses a parallel twin, knows what he wants: a full, throbbing steam hammer pushing out of the cellar with a robust sound and similar expressions of life in the form of noticeable vibrations. Or, to put it in the words of an old test of the Triumph Good city in MOTORRAD: “Whoever gets on a Bonnie does not expect a silky smooth run, whispering exhaust sound or impressive top speeds and the monotonous ceremony of pushing a button nowadays, driving off, hearing nothing, nothing He would hate to feel. ”The Triumph Bonneville (and the Tigers as well) have been committed to this claim for many years, since they saw the light of day in the late 1950s as the 650s and their character, regardless of all model updates and changes over the years has always preserved.

Tradition and modern technology from Japan

The Japanese, initially successful with two-stroke engines or later with powerful four-cylinder engines, also wanted to offer fans of this robust engine type something and combined the traditional design with modern technology. Can that convince purists, do the “copies” of Yamaha and Kawasaki come close to the Triumph “original”? Or should it be better to speak of Japanese interpretations of the British model? The comparison is a Yamaha XS 650 and a Kawasaki Z 750 B from 1977. The original is a Bonneville from 1978 – Triumph fan Peter Zeeb, who owns a proud collection of British bikes, has slow it to us. As a late example of the Bonnie series, it already carries all the changes and improvements: in 1972 the five-speed gearbox came (initially on request) (from 1973 series, since 1976 this has been switched on the left), in 1973 the displacement increased to 743 cm³ by enlarging the bore In the same year the primary drive came via a triple roller chain, plus the disc brake at the front. In 1976 the 750 was also fitted with a rear disc brake.

The cast wheels (from 1979) and the e-starter (from 1980), which are not particularly popular among purists, are not yet owned by our Bonnie and are old-fashioned without any modern frills. But Peter’s triumph is not completely original either: It carries the widespread, much better sounding roadster exhaust bags, the taillight of the old 1972 model and instead of the Amal carburetor, 32 mm flat slide carburetors from KOSO prepare the mixture here. "That was a tip from a buddy, they should work well, they said".

Triumph Bonneville 750 with a rich bass

We will see. It’s all about starting – carefully pull up the two choke buttons for a cold start, and, as the following days turned out, the twin of the Triumph Bonneville 750 jumps cold and warm on the first, or at the latest, the second step. Yes, the bystanders also get a flash, that’s what a twin should sound like. Sufficiently muffled, rumbling with a full bass when standing, thundering with light thrusts of gas and clearly audible, but not annoyingly loud – that’s it!

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In MOTORRAD 20/1978 the facelifted Bonneville was subjected to a detailed and critical test.

Swing into the comfortably low saddle, fold in the protruding side stand (no clicking spring – very commendable), put your hands on the wide, sweeping handlebars and enjoy the pulsating engine. The sitting posture with the upper body straight, the feet on the pegs placed far forward and the wheelbarrow-like handlebars almost give rise to chopper associations compared to the arrangements on the two Japanese. The sporty driving style that sets in on the winding roads of the small streets in the French hinterland where we are driving immediately belies these thoughts. Tea crisp transmission, which can be shifted over short distances, requires a bit of force and effort, but more and more often the higher gear simply stays in the tight bends, and the rich, smooth and easily controllable thrust with which Bonnie flicks out of the curve drives the grin on your face more than once.

The aged construction with two underlying camshafts, bumpers and cast iron cylinders is ultimately not made for high speeds and thus nothing for high continuous speed or permanent speed orgies. On the somewhat imprecise Smiths watches with the wriggling hands, the speed and engine speed can only be roughly estimated – the thrust sets in somewhere from 2,000 revs upwards, increases evenly under wonderful thrills, somewhere around 5,000 rpm you tend to shift because it is in the next course continues with good taste. Whether the 49 hp are fully available at 6,500 rpm is less of interest than the maximum torque available at 5,500 rpm. With its help, the Briton can accelerate out of the bends wonderfully clean, the two disc brakes are used before the next bend.

Well distributed, light weight

The Lockheed saddles grip surprisingly hard if you pull the brake lever courageously, the rear system supports the single disc at the front as much as possible. The sturdy chassis does not stand in the way of a sporty driving style, the thick central tubular frame with double loop undercarriage cannot be disturbed. The low, well-distributed weight the Triumph to fold easily into an inclined position and, despite the large 19-inch front wheel, it is pleasantly easy to turn.

Above all, the great precision when aiming at the line and the high directional stability ensure confidence and great fun on bends. The fork, which was again slightly improved for 1978, helps keep the front wheel on the ground on bumpy surfaces with decent response and good damping. The dry acting struts bounce back, but by no means spoil the fun. Fortunately, the Dunlop TT 100 tires, which were once standard, have long since given way to new slippers – today the Triumph, all patriot, rolls on British tires from Avon. Not always the hit when it comes to ultimate grip, but it is definitely enough for the hip driving style here, i.e. fast, smooth rolling. Especially since in left-hand bends, the hand stand that touches down with scratching noises reminds you to exercise moderation. So stay cool, exercise British restraint.

Kawasaki Z 750 B massive looks

Can the two Japanese twins keep up in terms of driving fun? The comparatively young Kawasaki Z 750 B, it came on the market in 1976, is impressive even when it is stationary. And with sheer size – it looks massive, huge in comparison. And it reveals itself as such with a Kawa-typical family design, even if the record-breaking huge side covers and the rear apron are more angular, more angular than, for example, the four-cylinder sisters of the Z family. There is no shortage of other Kawasaki models by Ralf Gnatzy, who owns the 1977 model year 750 twin shown here. It found its way into his garage twelve years ago, but has been moved far too seldom since then.

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Those looking for smoothness will find it in the Kawasaki Z 750 B. Acoustically, too, the engine is more than restrained.

That will change today. The photo rides with Ralf in the saddle have been completed, now I’m taking over the Kawasaki Z 750 B to collect my driving impressions. The engine is warm, so there is no choke aid. Simply turn on the ignition, take a look into the neatly drawn, Kawa-typical cockpit – after all, there is also an idle display here. A half-hearted first kick without any final determination lets the Kawa fizzle out unimpressed. Okay, then the hard way – the Bonnie required less strength. The second step works, which, unlike the British, does not have a long stroke, but an exactly square engine. But you can feel that you don’t feel anything. The technically complex dohc twin not only impresses with its slide-bearing crank drive, but also with high-tech solutions. Two counter-rotating balance shafts, driven by a chain, train the twin from the vibrations, allowing it to run almost completely free of vibrations.

A twin with the smoothness of a six-cylinder – was that the goal? Well, if you are looking for smooth running, you will find it here. The acoustics of the Kawa engine are more than restrained, a well-muffled, panting babble, not much more escapes from the two thick chrome pots. Two or three throttles prove how well and directly the twin hangs on the gas – so let’s go with the massive load. Higher seating position, higher and at the same time narrower handlebars, relaxed knee angle – everything about the Kawasaki Z 750 B is more powerful, and the sitting posture is more elevated at the same time. The clutch, which only engages very late, is easy to dose, with little gas and without a riot, the Japanese starts moving and doesn’t make a spectacle of her propulsion. It is by no means without it, the 750er can be accelerated completely smoothly from just over 2,000 rpm, at almost 3,000 turns it seems to unpack the torque club, but already at 4,500 the forward thrust subsides a little. Although the twin is still increasing its speed, it seems rather tough. I do not find the once-praised revving pleasure here.

Kawa with absolutely stoic directional stability

But it doesn’t have to be today either, after all, the Kawasaki Z 750 B stood still for a long time and shouldn’t be unduly abused. In the lower and middle range, the engine develops its typical design power and it is fun to savor the tangible thrust. The gears can be changed inconspicuously and easily, the initially noticeable higher weight of at least 235 kilograms with a full tank is put into perspective when driving through the first bends. The Kawa turns in unexpectedly easily, does not fall super easily, but willingly in an inclined position and does not annoy with wobbling or pendulum. However, it does not offer the absolutely stoic directional stability of the Triumph, a little concentrated it wants to be kept on course.

The Japanese also has to admit defeat to the British when it comes to brakes. Its single disc at the front is dull in its effect, wooden in its response and still requires a lot of hand strength. A second disc could help here, as the corresponding holes on the right fork sliding tube are already there. The rear, somewhat poisonous gripping pane is of only limited use. The fork, on the other hand, does a decent job – it responds very sensitively and offers a good middle ground, neither too tight nor too spongy. In a comparison of characters, the Kawa stands for the large touring motorcycle segment, while the Triumph clearly stands for the sporty roadster segment. The Kawa offers more massive size, but in 1977/1978 its opulence at 6,500 marks was also around 700 marks more expensive than the British.

Yamaha XS 650 – a bargain?

With a former purchase price of just under 5,600 marks, the Yamaha XS 650 from 1977 almost looks like a bargain. Does it offer less value for this? It’s not the first attempt that Yamaha has made with the XS 650 to compete in the league of parallel twins. The predecessors XS 1 (from 1969) and XS 2 (from 1971) already offered the same engine basis, i.e. a completely modern engine with roller bearings compared to the British model with an overhead camshaft that actuates the two valves per cylinder via rocker arm. A real rough leg that vibrated roughly, but otherwise satisfied. But the driving characteristics were more than poor and worlds away from those of a triumph. So Yamaha did the only logical thing – they hired Percy Tait, a British “defector”, who had previously worked for Triumph as a racing and test driver for years, and commissioned him with the development work. The result was the successor, now called the Yamaha XS 650, which replaced the unsuccessful TX 750 that had been offered in the meantime. And because the engine, thanks to the compression ratio reduced to 8.4: 1 and the lighter pistons, now showed better manners, the British could stand up to them. Gold?

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As heralds of a renaissance in two-cylinder technology, the "Poltermen" Z 750 B and the XS 650 in the comparison test in MOTORRAD 20/1977.

To find out, we asked Nico Streblow, a colleague and freelancer at MOTORRAD, to accompany us with his Yamaha XS 650. He has owned his XS since 2010, had a few things renewed, improved and revised immediately after buying it, and has since covered around 4,000 trouble-free kilometers with it. Even on the outside, it comes quite close to the English style and pleases with an elegant, straightforward and not too bulky appearance. The aluminum high shoulder rims look great, the standard double disc brakes and the tidy, clear cockpit are modern Yamaha standards at the time. Like the Kawasaki Z 750 B, the Yamaha XS 650 has an electric starter, but if the battery is not full and the engine is cold, it often only struggles for a short time, but in vain. So operate the choke lever on the 38 Mikuni constant pressure carburetors and step. The Yamaha also jumps willingly on the second attempt, needs a little less force than the Kawa, but with a bit of emphasis. The XS-Twin manages without a balancer shaft, does not shake as untamed as the Triumph engine, but it always delivers more expressions of life than its Kawa counterpart – noticeable and audible. The Yamaha immediately catches the eye with its seat height and its significantly higher weight – it plays more in the Z 750 than in the Bonneville league.

The sitting posture could come from a textbook – a more classic male driver posture is hardly possible. The line of the upper body, thigh, lower leg – right angles everywhere. So you sit upright, and yet compact, very close to the comfortably shaped, not too wide handlebars, downright active driving. The all-too-soft, somewhat spongy bench seat doesn’t quite fit – the good knee grip on the narrow tank helps prevent it from wobbling around. The finely adjustable, smooth-running clutch and the gentle use of power from the very bottom make moving off child’s play, upshifting in the crisp, engaging transmission with short shifting travel is a pleasure. The well-damped and pleasantly roaring twin can be accelerated from a good 1,500 rpm, accelerates evenly and unfolds its power most beautifully between 2,500 and 4,000 turns, without any real outburst of temperament. He doesn’t really want to be forced above 5,000 / min, at the latest from 6,000 / min something then only works with an unwilling roar.

Sitting posture on the XS got very British

The strength of the Yamaha XS 650 lies in its evenness and balance. The fine, annoying tingling vibrations that the Twin sends to the handlebars and seat, especially between 4,000 and 5,000 rpm, don’t really fit the robust two-cylinder: You would expect comfortably pumping bass frequencies here instead of high mids. You could also expect more from the double pane at the front. It requires a lot of hand strength and then delivers a decent delay, but no concrete bite. It is also very bony and moderately dosed. The rear drum brake does its job well – so it doesn’t always have to be a disc.

The once newly developed undercarriage with the cross tube and the additional reinforcements between the beams (for European models) cannot be deterred in normal operation, at most the rear can be set in harmless stirring movements at higher speeds. The design of the geometry is well done. The handling is impressive, the 650 steers easily, falls willingly on an incline and requires less effort in fast changing bends than you would have expected given the 225 kilograms. Nevertheless: The XS doesn’t follow the line as precisely as the Triumph and seems a bit nervous. It’s not because of the tires – Nicos XS wears brand-new, modern youngtimer tires. The previous owner has probably already worked on the suspension elements and swapped the standard suspension struts for Konis – a good decision. Like the fork, they speak a little stubbornly, but nothing swings back, nothing pumps – this way, even rumbling slopes can be confidently taken under the wheels. Is everything okay then? Well, admittedly – the last bit of steam and above all the real, rustic twin feeling is missing a little. The sound fits, also thanks to the retrofitted exhaust pipes, also in roadster styling, the handling pleases, the sitting posture turned out very British.

Conclusion

Are the two Japanese now getting the hearty, pure experience of the traditional English twins? To be honest, no – not in terms of engine sound and feel. Even if both have their own charms and at least the old (comforting) praise applies to the Yamaha XS 650: "The most English motorcycle that the Japanese have ever built."

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