Aimed at the traditional British buyer, the XS-1 was a polyglot machine that remained in production for 13 years.
Legend has it that the machine that became the Yamaha XS1 was nearly a Triumph. This would suggest that the ultimate form of surrender by the formerly omnipotent British industry would have been by marriage to the aggressor! It seemed that as the ‘seventies dawned Triumph’s US distributors were increasingly perturbed at just how long they could go on flogging the old parallel twin – a design already over 30 years old. New and exciting models were springing up everywhere – the DOHC Honda CB450 and the then-mind boggling CB750 four, big capacity two strokes from Suzuki and Kawasaki (both rumoured to be working flat out on four stroke multis), and even commendable efforts from some of the remaining European manufacturers. Yamaha, the stronghold of high-performance two strokes with many world championships already to its credit, was now working closely with Toyota and designed a 2-litre six cylinder DOHC engine for a proposed sports/GT car, as well as a SOHC 1600 cc four cylinder engine that powered the Celica series. In October 1966 the GT car set a stack of world speed and endurance records, including 78 hours continuous running at an average of 128.8 mph including fuel stops.
Mindful that the anti-pollution lobby in the US had the smoky two strokes in its sights, Yamaha used its new technology to develop a 653 cc air-cooled parallel twin with a single overhead camshaft. This engine actually had its roots in the long-defunct Hosk 500 cc twin which was first seen in 1955; the Hosk design owing much to the well-built 500 cc German Horex twin. Hosk was later acquired by the Showa Corporation, and many of the Hosk engineers found employment at Showa as well. Showa continued production of the 500 twin, and during the period before Showa became part of Yamaha in 1960, the engine was redesigned to 653 cc. Even at this stage, Yamaha’s bosses were reluctant to abandon their signature two-strokes, much as Honda was similarly reluctant to swing from four strokes to two strokes when it wanted to enter the motocross scene a few years later. Hence the discussions with Triumph US, and the belief that tests were carried out in secret. The Brit bosses however, did not buy the idea, putting their faith in the 750 triples and a wheezy 750 cc version of Edward Turner’s Speed Twin. Original Yamaha factory shots of the new motorcycle even showed the absence of the Yamaha branding on the engine’s side covers, just in case the Triumph deal had gone through.
And so it was that in 1969 the new Yamaha XS-1, the company’s first four-stroke motorcycle, was launched, with Australia one of the first export markets. Perhaps correctly, Yamaha reasoned that the Brits would be loath to abandon their allegiance to home-spun twins, and Yamaha did not go on sale in Britain until late 1971. It was also competing with the CB750 in major markets, although a price advantage (the XS-1 was launched in Australia at $1129, slightly cheaper than the Honda) helped it make inroads. One market that the XS-1 did grab was the police department in several countries around the world. It had enough speed to do the job and the traditional design fitted the bill well.
The original XS-1, in a fairly unattractive shade of green with white striping, sported a twin leading shoe front drum brake, kick starting only, and a conventional British-style front fork with outside springs concealed by rubber gaiters. First displayed to the world at the 1969 Tokyo Show, it was a machine that polarised opinion from the start. Naturally, the Japanese upstart was directly compared to the British twins from Triumph and Norton, both of which handled considerably better. The XS-1 vibrated like a British twin, and sounded like one with its 360º crankshaft, but was oil-tight thanks to unit construction with horizontally-split crankcases, and held its tune well. Due to the much lighter flywheel action (although it actually had four flywheels) than the British twins, the XS-1 responded to the throttle much quicker, but with a trade-off in torque. The pressed-up crank ran on three roller bearings and a single ball bearing on the right side. It wasn’t a bad looker either, with long reverse cone megaphone silencers and a neat slimline petrol tank.
It’s somewhat of an understatement to say that handling wasn’t the strongest suite of the XS-1, due to a combination of factors. The bearings used in the steering head and swinging arm pivot were not up to the job of coping with the stresses imposed by the big twin, although both these shortcomings could be addressed in later years with after-market replacement components. Perhaps the biggest impediment to stability was thew way the power unit was mounted in the chassis. Both front and rear engine mounts were simple plates and bolts, allowing the unit to twist under torque forces and naturally encourage the wheels to adopt their own passages. Gradually these problems were addressed in later models. Importantly the front mount became a strong box-section unit that stiffened the lower frame cradle considerably and reduced torsional flexing. At the rear, a saddle-shaped mount, welded to the vertical frame tube behind the gearbox, pulled that section into line, while the swinging arm pivot box-section on the frame itself was beefed up.
The XS-1 arrived in sufficient quantities to qualify for the inaugural Castrol Six Hour Race in 1970. Two were entered; one by Team Yamaha (McCulloch of Australia, NSW distributors) for Ron Toombs and Eric Hinton, and a second by Geelong dealers Pratt & Osborne for Allan and Graeme Osborne. The Toombs machine came to the line complete with the standard American-style high-rise handlebars, while the Osborne entry opted for a set of flat handlebars. Despite the wayward handling, both bikes qualified well and showed that the good fuel economy would be a factor in the race. Ironically, just after Toombs took the lead in the second hour of the race, the engine expired with a seized gudgeon pin. Perhaps as a result of this failure, a plain bush replaced the needle roller little end in subsequent models. The Victorian XS-1 ran smoothly to the finish, albeit ten laps down on the winning Triumph Bonneville.
Within a short space of time numerous after-market accessories began appearing, notably big-bore kits that took the capacity close to 750 cc, along the lines of the successful Flat Track racing version produced in the US for the likes of Kenny Roberts. Higher-performance camshafts and valve springs were also popular modifications. The XS-1 unit (with its five-speed gearbox) was also keenly eyed by the racing sidecar brigade, as it made an ideal replacement for the venerable and almost universal Triumph twin.
In the Australasian market, the original green and white model, of which 6,586 had been built was replaced inside a year by the XS-1F, which, apart from the gold and white décor, was almost identical except for a new front fork that had the springs enclosed in the stanchions and did away with gaiters. Other countries received the XS-1B.
A major technical change came with the XS-2 of 1972 (the first model to be sold in the British market), with electric starting and a single disc front brake to replace the out-of-fashion drum. Virtually all the XS-2s sold here were a candy orange with black stripes, although a few maroon models found their way in. To employ the electric starter, a lever on the right handlebar was engaged, which activated a decompression cable working on the exhaust valve of the right hand cylinder head. A safety device prevented accidental engagement of the starter while the engine was running. The balance factor of the engine was also changed and the handlebars and footrests were rubber mounted. The front mudguard was now longer and of more conventional shape.
By 1973, Yamaha was vigorously trying to recover from the debacle of the TX750 launch, the 750 twin having been joined by a smaller sibling, the DOHC four-valve TX500. To keep the family spirit, the XS-2 became the TX650, in metalflake blue with metal tank badges, but few other changes from the model it replaced. Logically, the following year’s model was the TX650A, which used a revised frame with tubular loops rather than straight pressings for the passenger footrest and muffler mounts. Colours were Vega green and Cinnamon brown.
With the demise of the TX750 and TX500, the 650 became the only big twin left in the Yamaha line-up, and as if to finally expunge any memory of the TX family, it became the XS650B (the XS650A was not released in Australia). Apart from the valanced alloy rims, black and gold décor was the only external change, but inside the engine, the valve seats were of a new material designed to accept unleaded petrol. For 1976, the XS650C was also identical save for the relocation of the front brake calliper to behind the fork leg and the option of red or French Blue colours. The XS650D, released in 1977, had the rear shocks beefed up, while front fork travel was increased 20 mm to 150 mm. Bountiful Blue or Maxi Maroon were the colour options.
Following the little-changed XS650E of 1978, the machine that had began life as the XS1 nine years earlier underwent a major redesigned – appearing as the ‘Specials’. Gone was the traditional mock-British styling, replaced by a chopperised look with 19-inch front cast alloy wheel and a similar 16-inch unit behind, with a disc brake replacing the rear drum. Engine-wise there was little change, but breathing was now via twin 34 mm Mikuni constant-velocity carburettors. A new, heavier-gauge frame with a longer swinging arm gave more predictable handling, and not before time. There were styling changes for the next three years, including reverting to a drum rear brake with spoked wheels for the 1980/81 Special, but the 1982 model, back to cast wheels, was the end of the line.
Its replacement, if that is the right word, was the first of the new-style fours, the XJ650, known as either the Seca or the Maxim, which shared the styling of the XS650 Specials, but with little of the character. And it certainly could not have been a Triumph either.
Geoff’s Shed: XS1 shrine
The featured machine you see here is just one of perhaps 30-odd complete Yamaha 650s in Geoff Bamford’s premises in western Sydney, the difference being that this XS1 is still brand new. The 2 miles on the odometer have been racked up by pushing the machine in and out of the shed, since it has never been started, and probably never will, at least by Geoff, who has refused several offers to sell it. Geoff came across the bike, a 1970 model, when Wayne Ulbrich closed his Yamaha dealership in Wollongong around 16 years ago, and simply had to have it. He already had several of this model, in fact he has several of every model, but this virginal XS-1 was certainly unique. In the eight years since he moved here, Geoff’s Shed has become the centre point for the XS (650cc) movement in Australia, and it’s bigger than you would imagine. Geoff builds bikes to order, from pristine original specification examples of various models, to all kinds of special order hybrids. He is currently completing an all-white ex-WA Police model which was mainly used for ceremonial duties, but scattered around the establishment are choppers, bobbers, flat-track styled road bikes plus lots of examples of racing dirt trackers, outfits (the engine was a very popular motocross sidecar unit in Europe) and specials that defy categorisation. I even spotted a beam-frame Suzuki where the XS650 engine had been slotted in so neatly you’d swear it was an original.
And then there’s the spares. Vast racks of frames and wheels line the walls, there are tanks and side covers of all hues and styles, shelves and shelves of engine components, posters, memorabilia – you name it. Geoff collects everything to do with the model, particularly important restoration stuff like switches, lights, instruments and so on. Not surprisingly, he’s a walking encyclopaedia on the model, with intricate knowledge of every subtle change between years, and the ability to spot European and US models from the domestic machines.
The XS range is more popular now than ever, and with good reason. They make excellent rally bikes, and the modern tweaks such as electronic ignition and carburation and suspension mods mean they are utterly reliable and very rewarding to ride. You can contact Geoff on 0412 677739 or firstname.lastname@example.org
Specifications: 1970 Yamaha XS-1
Engine: SOHC parallel twin with 360-degree crankshaft, air cooled.
Bore and stroke: 75 mm x 74 mm
Capacity: 653.3 cc
Compression ratio: 8.7:12
Carburettors: 2 x Mikuni BS38 SU-type.
Power: 53 hp (38.5 kW)@ 7,200 rpm
Torque: 38.4 ft.lbs (52 Nm) @ 6.000 rpm.
Transmission: 5-speed, wet multiplate clutch, chain final drive
Tyres: Front 3.25 x 19, Rear 4.00 x 18
Seat height: 810 mm
Wheelbase: 1435 mm
Fuel tank capacity: 14 litres
Dry weight: 186 kg (409 lb)
Top speed: 115 mph
Price new: $1129.00
Story and Photos: Jim Scaysbrook