In 1968 British industry finally launched the Triumph Trident and BSA Rocket 3 only to be aced less than a year later by Honda's seminal CB750/4. Set against this background an upstart firm that had made its mark with two-strokes launched an all out assault on the American market in a move that even now seems either amazingly brave or stunningly foolhardy.
Prior to 1968 and the invention of the sobriquet 'Superbike' a real performance machine was generally taken to be a British 650cc parallel twin and Yamaha decided they were going to have a slice of the action. The American market was huge, big Brit twins were still just about ruling the sales figures and there was no reason why a Japanese company that had been selling successfully for seven years shouldn’t succeed. Hamamatsu was going to take on the world.
Enjoy more Classic Motorcycle Mechanics reading in the monthly magazine.
Click here to subscribe & save.
There are lots of tales of how Yamaha came to make a parallel twin and probably there’s more than a grain of truth in all of them. We know the Japanese were influenced by European design and the German Horex Imperator is said to have made a definite impression in Japan. The Hosk Company had a sohc 500cc parallel twin in the mid to late 50s and when the Showa bought Hosk the model was carried over.
When Yamaha bought Showa of course the design was transferred to the new owner; or so goes one line of thought. It is also known that Yamaha worked closely with Toyota to produce the engine for the latter’s GT2000 sports car. It’s said that it is not coincidence that the engines of GT2000 and the XS1 share many common dimensions.
We know for certain that the Yamaha prototype borrowed the gearbox layout and frame from the YR1 350cc and that the company’s perceived knowledge was gleaned from a decade and a half of producing two-strokes. Certain sources close to Yamaha’s European base in Holland have stressed that the Horex and Showa links are extremely tenuous and it’s the Toyota route that carries the most credibility and this is now generally acknowledged as the correct genesis of the XS1/XS650.
In 1970 there was still a very strong following for big parallel twins as many riders didn’t want or trust multi cylinder technology. Yamaha’s new baby simply had to sell or the company was likely to be in a very serious financial situation from the start-up costs of going four-stroke.
History shows the design was an absolute star right out of the crate and by the time the curtain came down on the big twin in 1985 Yamaha had shifted an alleged 850,000 units. As an aside it’s said the only reason they stopped making the XS650 was to give the new XJ650 four-cylinder model a fighting chance to establish itself.
Over that 15 year model run the bike would be restyled, receive an electric start, have three different engines designed around a common theme, acquire upgraded frame based on Triumph race track knowledge and spawn what later became known as the factory custom look. However, this month we are enjoying the first two models of the production line; the XS1 and XS1B.
The XS1, known to followers as The Green Granddad, is one of some 5000 from the first year of manufacture and as rare as they come. The XS1B is from the following year and carries a host of minor revisions along with an obvious change of colour. Often the gold paintwork on many XS1B models looks washed out and faded due to UV degradation of the coloured candy lacquer but our test bike, belonging to Chris Pile, is simply stunning following a total restoration using modern paint technologies.
The green of the XS1 is pretty much all original save for bit of accident repair work. What is totally unavoidable is the reaction that both bikes create whenever they are parked up. During our early evening photoshoot more than a few slacked jawed motorists were observed rubber-necking at these two stunning examples. Even non-bikers appreciate candy paint and chrome apparently. The same effect was precipitated when we plotted up for a drink later at a local hostelry. “Nice bikes lads; they're not British are they? My old dad used to have a Beezer, looked just like them it did”. Ride up any parallel twin that makes the right sounds and everyone’s spectacles or shades take on a rosy hue.
A quick look around the bikes reveals a unit lump with a single cam carried in four of the biggest roller bearings ever to grace the valve gear of a bike engine. The bottom end of the motor is similarly over engineered and this approach to making their first four-stroke earned Yamaha the reputation of producing a power unit that could almost withstand a direct artillery hit.
From the rider’s viewpoint two large chrome and black clocks dominate the top yoke while a neat alloy filler cap with the corporate logo crowns the fuel tank. Both bikes feature shrouded rear shocks (the XS1B actually sports a pair of Hagon units) but the front ends differ. The earlier bike has rubber gaiters over external fork springs. The later bike has what was called at the time Ceriani type forks with the springs inside the stanchions and the bare hard-chromed legs exposed for all to see, presumably in the name of fashion. The later machine also has revised fork internals; a reflection of the company’s search for continuous year on year improvements.
The green XS was never built with indicators, these were an optional extra. The yellow-gold 1B has indicators as standard and this is one of those grey areas that gets XS650 aficionados enthusiastically debating in the pub. The post XS1 yellow 650s that precedes the XS2 of 1972 actually came in two guises, the XS1B and the XS1F.
'The XS1B followed the XS1’s optional extras in locating the front units on pressed metal arms atop of the fork nuts of the top yoke; the XS1F is said to have the front indicators mounted on the more traditional headlamp brackets. But enough pedantry; suffice it to say that either model is rare beyond belief and drop dead gorgeous into the bargain.'
However, both models are generally referred to as the XS1B yet factory records clearly show a different series of engine numbers for each of the two models. It’s argued that one of the primary differences was the use and location of the indicators. The XS1B followed the XS1’s optional extras in locating the front units on pressed metal arms atop of the fork nuts of the top yoke; the XS1F is said to have the front indicators mounted on the more traditional headlamp brackets. But enough pedantry; suffice it to say that either model is rare beyond belief and drop dead gorgeous into the bargain.
Both bikes have metal side panels with chromed plastic 'C' flashes similar to and reminiscent of 70s chromed bathroom fittings. The machines may have been sold as the XS1/XS2 etc but Yamaha were actually calling them XS650s using chromed mazac badges to emphasise the point. Perversely the name XS650 wouldn’t be used to sell the company’s biggest machines until 1974 yet the bikes already carried the logo.
Starting on either machine is by kick only; an electric foot appeared on the XS2 but not without a lot of pain. Yamaha had to reduce the sump capacity by half a litre to get the starter motor under the back of the gearbox and build one of the most tortuous transfer gear systems known to man. Sometimes the demands of fashion can lead to unsatisfactory compromises.
There was a very definite belief that the bikes were destined for long distance use as evidenced by the long comfortable saddle and the usefully sized grab rail. To further increase long trip viability the bikes also utilised rubber mountings in ways that would have been an anathema to Armoury Road or Bracebridge Street. The XS1 range was designed to be ridden hard and long and this is exactly what the bike excelled at; short of crass abuse or an absence of oil the average rider had to try incredibly hard to kill one of these motors.
If you were to camouflage both bikes, remove their obvious visual differences and hand an average test rider the keys it’s a fair bet that they would be hard pressed to tell the XS1 and XS1B/F apart. They may be a year apart but most of the differences are engine and paint scheme based. Both bikes have a very sharp pick up on the throttle giving the impression that there’s a very direct link between the rider’s right hand and the rear wheel.
The power delivery is best described as confidently pokey and whatever else the early XS1s might have lacked they certainly managed to capture that classic 650 parallel twin grunt. Come out of a corner and as you open the throttle the bike surges ahead in an instant with a beautiful roar from the silencers that even contemporary testers viewed as being on the loud side of acceptable. One area where the Yamaha bettered our home grown twins was in carburation.
'While home grown Amals would have gradually degraded in fuelling accuracy as the poor quality die cast alloy fretted away, the Yamaha’s high silicone content bodies and hard anodised slides just shrugged off countless miles.'
Sporting a pair of 38mm CV Mikunis the engine gets exactly the fuel it requires, no more and no less, thanks to the laws of physics and manifold depression/vacuum. Another bonus, though probably not apparent for several tens of thousands of miles, would have been carb wear. While home grown Amals would have gradually degraded in fuelling accuracy as the poor quality die cast alloy fretted away, the Yamaha’s high silicone content bodies and hard anodised slides just shrugged off countless miles.
It’s always been argued that until Percy Tait reworked the chassis of the XS2 the Yamaha was a poor handler. Some went as far as to suggest that the XS1 and 2 were little short of widow makers; such is the power of urban myths. A marked rearward weight bias, some potentially questionable geometrics and a lack of bracing to certain key areas all conspired to give the XS1 and 2 variants a minor notoriety that was latterly blown out of all proportion.
To some degree the bikes were more than a little flaky when pushed to the absolute limit or run alongside a featherbed Norton. Under researched suspension systems, poor tyre design with dodgy compounds, a rearward biased weight distribution and a weakly braced frame all conspired to give a less than ideally handling package.
Fast forward to 2009 and neither bike actually feels that bad; ridden with just a modicum of common sense neither machine gave the slightest cause for concern. Even ridden fairly hard on the winding roads around the hills of Hampshire there were no problems. Obviously we cannot go out of our way to provoke an adverse reaction from someone else’s bike but riding with Peter Spicer (owner of the green XS1) on either machine never gave this test pilot any heart stopping moments.
Treat either bike as you might a Fireblade and doubtless you will have a moment or several; ride sensibly the way you would on your own treasured classic and you begin to wonder what all the angst was over. Peter and Chris both feel that modern tyre construction is probably the single biggest improvement an owner can make to these machines and US road testers certainly experimented with alternative rubber resulting in varying degrees of improvement.
Stopping that mass with a TLS front brake isn’t drama packed but it’s easy to see why the next iteration of the range (the XS2) came with a twin piston calipered disc. Ridden to the limit a drum brake that owes more than a nod to the front stopper of Yamaha’s 350 two-strokes will ultimately suffer from fade.
Some have argued that the early XS Yamahas are flawed gems and that the pinnacle was only reached in the mid 70s with legendary 650B, C, D and E models. Post XS2/TX650 the USA and Australia were graced with 447 series motors designed to give greater pick up at lower engine speeds that matched the desire for traffic light grand prix and fast standing quarter times.
Europe received 533 series engines that were aimed at higher top speeds and greater top end performance. Both engine types covered themselves with glory in a variety of sports as well as general road use but never quite had the same gutsy feel as the original 256 series lump that graced the early machines. As is often the case first-off models are commonly viewed as the best of the breed and it’s a maxim that few could rationally argue against with the bikes on these pages.
Flawed gems? Hardly. Think of an XS1 as a very slightly rough diamond; full of character, a cheeky grin, thoroughly likeable with a little bit of attitude and an occasional hard edge response and you won’t be too far off the mark. It’ll take a remarkable amount of abuse and is unlikely to give you a good hard slap in return unless you grossly abuse its good nature. A day out with one will remain unforgettable, guaranteed.Enjoy more Classic Motorcycle Mechanics reading in the monthly magazine. Click here to subscribe.