On the move: Yamaha XJ 650

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On the move: Yamaha XJ 650

On the move: Yamaha XJ 650

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The Yamaha XJ 650 inspired the motorcycle scene almost 30 years ago and is still convincing today.

A child of the 80s: the Yamaha XJ 650.

"She shows off neither fancy technology nor unnecessary gags. But the consistent use of the tried and tested, skilfully coordinated, results in a completely successful motorcycle." With this apt summary, MOTORRAD editor Peter Maierbacher summed up the character of the Yamaha XJ 650, type code 4K0, in issue 6/1980.

In fact, the new series, which was intended to replace the XS models, took center stage right from the start. Described by the Yamaha strategists as a sporty, high-performance motorcycle, everyday and touring riders increasingly resorted to the offer. The maintenance-free cardan drive was argument enough for many motorcyclists. The O-ring chains had already moved in, but the eternal anointing was still a tiresome act. Not to mention the dirty wheels and chassis. The XJ 650 engine has some amazing details: In order to limit the overall length, the Yamaha technicians relocated the transmission output shaft under the input shaft – a solution that manufacturers are now selling as a revolutionary construction for sports machines.

The endeavor to make the four-cylinder as compact and narrow as possible was followed by the piggyback alternator driven by a toothed chain, which is located behind the cylinder bank. The designers dispensed with a vibration-inhibiting balance shaft; Lush rubber mounts on the front engine mount decoupled the engine from the frame against high-frequency vibrations. Which did not change the fact that the air-cooled in-line quad tickled the handlebars and notches at speeds above 7000 rpm.

If you want to put Yamaha’s promises to the test and move the XJ 650 in a sporty way, not much is possible without high revs. On the one hand, the two-valve engine lacks displacement for full pulling power, and on the other hand, the 72 hp at 9000 rpm require an engine configuration that is geared more towards maximum performance than a wide usable torque range. Because for an air-cooled two-valve engine that also meets the noise limits, the specific 110 hp per liter of displacement is a solid figure. For comparison: the Honda CB 750 F (RC 04/1981), which appeared one year later, achieved 79 hp at 9000 rpm despite the displacement advantage and four valves per cylinder. That corresponds to only 105 HP per 1000 cm³.

It was not until later years of construction of the XJ 650 models that the Yamaha technicians used the YICS, which should bring advantages in terms of power and torque. Behind the Yamaha Induction Control System was an interference system, in which each cylinder sucked in fresh gas from the three other intake ports during the intake stroke. The inlet to the inlet channel was oriented at an angle and should cause a swirl, thus better turbulence in the fuel-air mixture.

However, there is no question about the choice of carburetor for the first XJ 650: The large 32 mm diameter of the Hitachi constant pressure carburetor installed at the beginning should contribute significantly to the high performance. A contactless transistor ignition ignited the mixture precisely. For valve control, Yamaha resorted to the construction principle common at the time with two overhead camshafts and bucket tappets with external shims for valve clearance correction. So that the air-cooled four-cylinder does not suffer heat collapse even in summer temperatures, there is an oil cooler underneath the heavily reinforced steering head, which dissipates the heat from the thermally highly stressed engine sections and also uses the lubricant as a coolant. After all, excessive heat gnaws not only at the stability, but also at the engine performance. On the other hand, the fact that the cardan should eat up a lot of power remains a rumor. Although the power flow is deflected by 90 degrees via two angled drives, the efficiency, as the Yamaha engineers assured as early as 1980, was only marginally worse than with a chain drive in optimal, i.e. new and perfectly lubricated condition.

Driving impression

The performance shows that the promised engine performance was not only available on paper, but also on the rear wheel. At an impressive 197 km / h, the XJ 650 ran through the light barrier during the type test by the TÜV. Helmet up and down the post. "After just a few meters, the seating position inspires, the height is also right, the well-shaped handlebars are just right." Peter Maierbacher’s impression is still correct 30 years later. In addition, it should be mentioned that the XJ shows a playful ease when turning, maneuvering and driving at walking pace, which is often missed these days. And that with a weight of 230 kilograms

"Neither the initiation of curves nor the holding in an inclined position requires effort. It takes all kinds of bends completely neutrally, whether angular or elongated." In 1980, the editor commented on the sporty note of the XJ 650. It will only wear it if you maneuver it through alternating curves beyond 100 km / h and the gyroscopic forces of the heavy cast wheels equalize the advantages of the narrow tires.

The standard spring / damper elements occasionally stop working on heavily undulating asphalt and defiantly trample through potholes and cracks of frost. Here, too, the Dutch Koni shock absorbers were effective: Touring riders in particular achieved acceptable driving stability and more suspension comfort with a full load.

With a tank capacity of 19.5 liters, the range of the XJ 650 was sufficient for the high demands of the touring group. The huge H4 headlamp, the acceptable pillion seat and the large lean angle that was still sufficient with a load sang the same song.

It is always astonishing how the Japanese technicians were able to cultivate their cardan machines in terms of driving and suspension properties. Even without complex torque support, the elevator effect of the XJ is limited. Which of course also has to do with the fact that the rear suspension travel is not even 100 mm and leaves little room for the up and down of the cardan.

"The braking system decelerates safely and without fading. The double disc brake would be completely without blame if it required less manual force. The drum brake works amazingly well, finely dosed and has a good effect." With which the excerpt from MOTORRAD 6/1980 also shed light on the subject of brakes. From a technical point of view, it’s no wonder that the single-piston floating calipers with a weight of 230 kilograms have a hard time. They work on small 267 discs with a corresponding gear ratio.

The XJ 650 set standards not only in terms of performance and handling, the MOTORRAD long-distance test over 40,000 kilometers also demonstrated a high quality standard. Only a broken piston ring left compression loss and a few question marks. But otherwise: everything is great. This motorcycle concept is still a lot of fun today (www.xj650.de), and many motorcyclists long for a modern re-edition.


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Technical specifications


Drawing: work

Two overhead camshafts, bucket tappets; the gear shafts rotate one above the other.

Yamaha XJ 650

Engine: air-cooled four-cylinder four-stroke in-line engine, two overhead camshafts, two valves per cylinder, bucket tappets, wet sump lubrication; Bore 63 mm, stroke 52.4 mm, displacement 653 cm³, compression 9.2: 1, 72 HP at 9000 / min, 59 Nm at 7500 / min, mixture preparation, four Hitachi constant pressure carburettors, Ø 32 mm

Electrical system: E-starter, battery 12 V, 12 Ah, contactless transistor ignition, alternator 12 V, 260 W.

Power transmission: Multi-disc oil bath clutch, claw-shift five-speed gearbox, gear ratio 2.178 / 2.500 / 1.153 / 0.933 / 0.821, secondary drive: cardan

Landing gear: Double-loop tubular steel frame, front hydraulically damped telescopic fork, rear two-arm swing arm with two hydraulically damped suspension struts, front / rear spring travel 150/96 mm, cast aluminum wheels with double spokes, front tires 3.25 H 19, rear tires 120/90 H 18, front double disc brakes, 267 mm, with single-piston floating pads, rear simplex drum brake, 180 mm

Measurements and weight: Wheelbase 1442 mm, weight 230 kg, tank capacity 19.5 liters

Driving performance: Top speed 197 km / h

Price: 7015 Mark (1980)

Manufacturer: Yamaha Motor Co. Lrd., Shizuoka-Ken / Japan

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