AN INDICATION OF THINGS TO COME? Suzuki's RE-5: the world’s first mass-produced rotary motor-cycle

Press, Volume CXV, Issue 33779, 27 February 1975, Page 13

AN INDICATION OF THINGS TO COME? Suzuki's RE-5: the world’s first mass-produced rotary motor-cycle

(By

R. O. DEW)

Is the remarkable Suzuki RE-5 rotarypowered roadster the result of an adventure in advanced technology or will it stand the test of time as an acceptable alternative to the conventional ?

The complete answer to this question will not be known until world market reaction becomes clear and that will not be for many

months yet. However, by spending millions of dollars on developing the rotary engine the princi- ; pals of the Suzuki com- ’ pany have indicated great faith in the future of this ' type of power unit for motor-cycles. Certainly, no new model has created greater interest in the last decade. Suzuki officials describe the RE-5 as the pioneer of a new age in motor-cycling; the critics claim that it has too many drawbacks to make it anything but a curiosity piece. The truth, undoubtedly, lies somewhere between these widely divergent views. But there is one thing which everybody must accept — the rotary-pow-ered Suzuki is a reality. It is the first of its type to be mass produced in the world — the assembly lines in Japan are now in full swing — and the first

shipment of 25 for the New Zealand retail market is expected any day. To all intents and purposes, these are already sold. But more will soon be on the way. New Zealand has been allocated 25 a month — a restriction made necessary by the initial heavy demand throughout the world. The RE-5 will sell in New Zealand for $2599 which, by today's standards, is not unreasonable for a machine of such a revolutionary nature. Although technically a 500 c.c. roadster, its power output and other “vital statistics” place it in the 750 c.c. class. As a comparison, the Suzuki GT7SO twostoke triple currently costs $2075 but is expected to rise shortly to about $2400.

FIRST IN N.Z. There is at present only one example of the RE-5 in New Zealand — the demonstration model used for the technical seminars held throughout the country to familiarise mechanics with the rotary engine. Tommy's Suzuki Centre, which now has the machine on display, lent it to “The Press*’ tor testing.

At first sight, the RE-5 is impressive. That alloy rotary engine looks big and powerful enough to drive a car. The styling is very futuristic, although it takes a little getting used to. Making the instrument panel container and the tail light tubular is, perhaps, carrying the rotary theme a little too far.

The RE-5 is a big machine, and heavy, too. The claimed dry weight is 5071 b (230 kilograms), the same as that claimed for the GT7SO, but the actual weight, tanked up, is closer to 5601b5. This is particularly noticeable when one attempts to drag the rear wheel round by hand to get the bike into a corner of the garage. But once mobile, the impression of great weight disappears. The RE-5 handles well at all speeds above walking pace. The centre of gravity looks high but the Suzuki has a very balanced feel about it

in spite of this. The seat is low and the riding position confortable. For touring, it is difficult to imagine a more suitable bike. The rotary engine has very little vibration and the power

characteristics are perfect for this use. The width of the power band is incredible. In top gear, the engine will pull from idling speed of 1500 r.p.m. through to the 7000 r.p.m. danger line. Throttle response is startling at maximum torque revolutions of 3500. Its low speed pulling power is unequalled by any other

roadster of comparable size in existence. Although its top end performance is less than stunning, it can top 110 m.p.h. and cover, a standing quarter-mile in 13.2 sec. ' The rotary is very’ much at home on hill work. It can bound up all but the steepest of slopes in top gear and with the engine idling in bottom can climb a one-in-three incline.

Rotary engines are not known for engine braking but the Suzuki unit does provide reasonable retardation. If one allows the engine speed to drop too low while changing down, the rear wheel will skid when the clutch is released. This has to be watched carefully, especially in wet conditions. With such a heavy machine, good brakes are essential. The Suzuki cannot be found lacking in this regard. The twin hydraulic discs at the front are powerful and require little effort to operate. The rear drum unit is also more than equal to the task it was intended for. MIXED BLESSING

On hot days, riding the Suzuki- can become a little uncomfortable. The engine casts off a lot of heat and much of this, perhaps because of the considerable width of the unit, blows back on to the rider. This would obviously be a bonus point in winter or in cold climates. An automatic cooling fan is fitted to the right of the radiator and this is very necessary to keep the engine temperature down in slow moving city traffic. One of the most appealing aspects of the rotary engine was supposed to be its simplicity and its compact nature. The Suzuki

unit is quite the reverse. It is a very complex machine indeed, far beyond the understanding of the average home mechanic. Even the two-barrel, two-stage carburettor cannot be tuned by anybody other than a qualified expert. However, the standard of manufacture of the engine is such that it should not require a major overhaul for more than 40,000 miles. One of the major teething problems was the high wear on the inner surface of the rotor housing. To overcome it, Suzuki per-

fected a new plating techinque. Extensive testing has indicated that the engine will normally last the life of the motor-cycle. A micro-analyser is used to assess the molecular structure of the raw materials used and tolerances within one-thousandth of a millimeter are maintained Because of the amount of heat generated by the single rotor engine, the cooling system plays an important role. Like the rest of the bike, it is somewhat complex. A dual system is used, with water cooling for the outside housing and oil cooling for s the internal engine parts. The water flows from the radiator past the hot ignition side of the rotor housing and then circulates through the relatively cool port side. This helps reduce the temperature differential between the two sides. The cooling oil, which also serves for lubrication, passes through its own cooling radiator located below the water radiator. TWIN SHELL EXHAUST The gasses exhausted by the rotary engine are of an extremely high temperature and this has to be reduced before they leave the exhaust system. The two exhaust pipes feature twin shell construction. Fresh air is introduced through openings at the front of each outer shell. This air cools the exhausted gas in the inner shell along the length of the pipe and is finally mixed with it just before it reaches the mufler tip. As well as lowering the temperature of the exhaust gasses to an acceptable level, the unusual exhaust system also provides an important silencing effect. Very accurate ignition timing is necessary for the rotary engine and this is provided by the capacitator discharge system. A speed relay and vacuum switch installed inside the mechanism are linked to permit feedback to the ignition switch. A double point system is utilised in order to provide optimum sparking throughout the speed range. Although essentially a 750 tourer, the RE-s's single chamber has an actual capacity of 497 c.c. The maximum horse-

power is 62 at 6500 r.p.m. Thia compares very favourably with the 50 brake horsepower of the Suzuki GTSSO and even the 67 brake horsepower of the GT7SU. _ Maximum torque of 54.9ft-ib t’.uuKg-m) is achieved at onlv 3500 r.p.m. Over-all, the Suzuki will average about 40 miles to the gallon which is better than a lot of the big two-strokes can manage. The 3.7 gallon (17- 1 litre) iue! tank gives the bike a range of about 150 miles, less if ridden hard. An electric starter is the only means of firing up tlie motor, although a kick leverlcan be fitted as an optional ■ extra. Tlie five-speed gearbox is the same as that used for the GT7SO and. although not achieving quite the high standards of the engine, is perfectly adequate. There was a slight clunklness in the lower ratios of the unit on the teat machine. GOOD DETAIL The instrumentation and' detail woik ou the KE-5 are quite outstanding The instrument panel contained within the cylindrical casing on top of the headlight provides a wealth of Information. As well as the usual speedometer and revolution counter, there is a temperature gauge, a digital gear change indicator and a row of six coloured lights. The low fuel lamp, the low oil and oil pressure indicators are alongside the turn signal repeater, main beam and neutral bulbs. When the machine is not in use, a transparent cover closes over the panel. This is released when the ignition key is turned into the first position, enabling the various circuits for the warning lights to be checked before a further twist of the key enlivens the ignition. It has taken Suzuki more than four years to design and produce the RE-5. The licensing contract to manufacture rotarv engines was concluded with NSU-Wankel in November, 1970. However, the time has been well spent. Pre-production models of the RE-5 covered more than a million miles in testing and the engines have been subjected to 24-hour, 100dav dynamometer tests. With this behind them, the Suzuki engineers are convinced that they have a winner. If sales prove them correct, the RE-5 will undoubtedly be the forerunner of a whole new range of rotary-powered motorcycles. This Is, indeed, an exciting prospect.