Venture in technology: the original Yamaha XZ550 V-twin
Le Moto journal 536, 24 December 1981
Most of this test
is translated by XZv2. Keep in mind that this is a test of a Euro-version of
the XZ 550 on a racetrack in
Remember I am not a
professional translator; my native language is Dutch, my knowledge of French is
limited.
Yamaha invited the European and the
Australian motorcycle press to Japan to discover three new models: the 550
XT, the 550 XZ and the Turbo 650. After the marketing offensive at the
Motorcycle Show in
The French MOTO Journal did make test rides on the brand-new
XZ on a racetrack in
Introduction
One observes that Yamaha relies totally on technology to attract new customers. The manufacture of two stroke motorcycles with liquid cooling for daily use is an example, but the conception of the XZ is another one. The Japanese technicians study systematically all the technical sectors of the motorcycle world. After the sophisticated two-stroke, after the four-stroke four cylinder, after the turbo, the XZ550 marks a tendency in the direction of the V-twin. This tendency started with the introduction of the TR1 and the XV 750 and 1000. No market-niche is neglected and in this way the motorcyclist can find every technical variation within a group such as V-twins. The wink is clear: Yamaha demonstrates that every type of engine, every technology results in an exciting motorcycle.
The test XZ550 in
Japan
The V-twin is a traditional engine type comparable to the
single cylinder. But it is not the “retro”-fashion that dictated this concept
to Yamaha, but more a remake of the Japanese motorcycle concept. It is no
coincidence that Yamaha listens to the European market, through her
headquarters in
The valves of this
engine form a narrow angle of 18 degrees: this gives a better “squish” effect
to the combustion chamber. The two large diameter carburetors have a nice, soft
control. The induction tracts are quite straight: the mixture goes straight via
the valves into the combustion chamber.
The XZ550
The XZ550 is a typical specimen of that new opening, that goes hand in hand with a charm-offensive towards the European market. Forget the number of cc and study this motorcycle well. She is small, compact, original as well in technical as in esthetical sense. Attention is drawn immediately towards her engine, that is as beautiful as it is plain (sobre). Yamaha introduces this motorcycle as a sports motorcycle. Certainly her engine characteristics (116 horsepower/liter) are impressive. Technically, this XZ innovates really (see captions of the photos and figures), but in a good way. The multi-cylinders are perhaps something of the past and this type of twin replaces it advantageous. Now the reliability of this type of V-twin in comparison with four-cylinders must be proven.
On the right side,
part of the frame is bolted on. This facilitates the removal of the engine
from the frame. Note the imposing air filter box that has a capacity of 6,4 liter. Because
of this box the gas tank is imposing, but that is to the eye only. The
access to the spark plugs is not easy. The engine fills the frame like an
egg.
The XZ on the racetrack: a special test.
The test of the XZ550 was on the private Yamaha racetrack. That is, under special conditions that do not correspond to every-day-use. On the track, one judges primarily the behavior at speed of the XZ. The riding position is surprising: much forward, a little bit as on the large capacity Hondas and that in spite of the lowest position of the handlebars (there are three positions) [French: très en avant, un peu comme les grosses Honda et ceci malgré la position plus basse des guidons].
The riding position, especially the pressure on the hands, is important, so it is necessary to try a motorcycle long-distance.
Up to now, Yamaha could not make as good shaft drives as the other Japanese makes. The loud clonc of the 1100 is famous just as the little one of the XJ650. Forget all this with the XZ: the gear box is perfect, the gears can be changed without clutch even when going down to first gear. One must be really brutal to lock the rear wheel.
The engine qualities are another positive point: this V-twin shouts of joy like a four-cylinder and has a better torque (French: ce V-twin a l’allégresse d’un 4 pattes et bien plus de couple).
The power-train of
the XZ is new for Yamaha: it has adopted the simplest principle quite good,
without any intermediary axle (a solution never abandoned by Suzuki, by the
way) .
Straight-cut gearwheels transmit the power from the crankshaft to
the clutch-gearwheel, at the right side of the engine. Power goes through
the secondary shaft of the gear box and is brought forwards again to be
transmitted to the final shaft. This results in a compact design. For that
reason also, the shock absorber is fitted at the level of the axle of the
rear wheel. The axle of the balancer is up front, driven from the
crankshaft at the left side.
In contrast: the advertised 64,4 horsepower do not translate into a better performance than the 58 horsepower of a Kawasaki GPZ550, and, even more so than the 58 hp of a 600 Ducati Pantah. The Yamaha’s top speed is 195 km (122 mph) and it needs 13,1 seconds for the 400 meters = quarter mile. That is also the performance of the GPZ. The Pantah is faster than 200 km (125 mph) and does the 400 m in less than 13 seconds. You understand even less of this when you know that the Yamaha is lighter than the GPZ and the Ducati… (but believe that the shaft drive eats more than 6 horsepower…….).
This is the information from the racetrack; in contrast, I am convinced that the torque of the Yamaha will make the difference with the four-cylinders in road use. In fact, this engine is more an engine for the road than for the race-track.
On the 350 RDLC, the rear suspension monoshock is nearly perfect. On the big V-twin XV750 and TR1-1000 on fights with the problems of the adjustment. It probably will be the same with the XZ. The few bumps in the racetrack have systematically caused waving, not dangerous, but not compatible with a bike that is labeled “sport”.
By hardening the rear shock absorber (4th position) the waves become less, but do not disappear. The XZ needs another, more efficient, rear shock. The comfort is less in the harder positions of the rear shock.
The front fork
with the axe mounted backwards is a new design also. At the inside it is
simple, without air support. This design limits
the length of the wheelbase and it results in a bike that is easy to steer at
low speeds.
For a real perfect road-holding, the front fork must also be better damped. We must wait a real test on the road to confirm the impression that low-speed steering qualities are not perfect. But the manoeuvrability is perfect, a real bike, it holds the road good, and on small winding roads, the mix manoeuvrability-torque-roadholding must be exciting.
I am forgetting the brakes. The double front disks are perfect, rear there is nothing: no risk to lock the rear wheel.
Summarizing: the XZ550 is announced as a sports-motorcycle. In practice it is more a sports-tourer: a compromise in all aspects. But, only a little bit is lacking to make it a real sports bike.
During this test, we could compare the performance of the XZ with the XJ650 Turbo. That bike is faster in top speed and in acceleration, the XZ is faster in leaving a (sharp) bend.
Technical data:
V-twin with 4 valves per cylinder. Double Overhead Camshaft driven by Hy Vo chain, for each cylinder. 552 cc, 80 x 55 mm bore/stroke.
Carbs: 2 36 mm diameter.
Wet sump lubrification, 3,4 liters content.
Forks: telescopic with a travel of 14 cm. Two front brakes with 226 mm diameter disks. Back: monoshock, 9 cm travel, 5 positions for tension of spring. Brake, conventional shoes, single lever, 18 cm diameter.
Max speed indicated by Yamaha: flat-out 195 kph (122 mph)/ seating 185 kph (115 mph).
XZv2
Postscript by XZv2: this test already indicated, in 1981,
that the XZ was not a super-sports motorcycle, but more a sports-touring bike.
That is, even before it was for sale to the public. In spite of these
conclusions, Yamaha marketed this bike as a supersport
in
It is remarkable that the French tester in 1981 in
Yamaha made the 1983 model with air support in the front forks, and the rear shock with adjustable damper. The French tester was a “visionary”!