A superb sports roadster from Yamaha

Press, 8 July 1976, Page 15

A superb sports roadster from Yamaha

By

ROD DEW

The new RD4OOC Yamaha two-stroke twin was hailed as the outstanding mid-range roadster of the year when it was wheeled before the public for the first time in Japan some months ago. Now, the first examples have arrived in New Zealand and it is evi dent that this lavish praise was not undeserved. It is by no means the perfect road machine and it will not suit everybody with its modern styling, cast alloy wheels and marked sporting characteristics. But for those who want their personal transport to be capable of providing something a little more exciting than the proverbial armchair ride it will have enormous appeal. No production racer can duplicate the performance of a competition machine but the RD4OO comes closer to this than anything else of its size on the market. The RD3SO, which it replaces, was acknowledged as the fastest machine in its class in production racing. The new model has about the same top speed of 160 km/h but it has a much wider power band, a sixspeed gearbox with closer ratios and superb brakes — independant hydraulic discs, back as well as front. It seems certain that it will take over on the production racing scene where the RD3SO left off. And this is hardly surprising. Both machines are direct descendants of the legendary Yamaha racing twins. But whereas the RD3SO was a rather "hairy” machine, the RD4OO is somewhat more refined. Apart from the wider power band, the tendency of the exhaust to smoke under heavy acceleration appears to have been cured and long reach spark plugs fired by higher output coils reduce the chances of oiling up in stop-start city travel. Improvements have been made in comfort. The seat has more generous upholstery, the handlebars are rubber-mounted and the redesigned fuel tank,

which is two pints larger, is easily gripped with the knees. In some respects, the appeal of the Yamaha is in its basic simplicity. The two-stroke twin, which now has a longer stroke and an actual capacity of 398 cu cm, will provide no new puzzles for mechanic.,. While other manufacturers have moved on to multi-cylinder two and four-strokes with upswept pipes, the RD Yamahas have retained their original theme. However, practically every item of equipment has been improved considerably. There is now, for example, a self-cancelling turning indicator system connected electrically to the speedometer. But the

cancelling device only operates when the bike is in motion. This is something which other manufacturers should copy forthwith. There is a headlight flasher for overtaking and, of course, a "kill” button. No electric starter is fitted but starting is easy, even when cold. The brakes are quite outstanding — light, positive and fade free. The test machine provided by Tommy’s Yamaha gave this tester his first experience of a disc brake on the rear wheel. Strenuous efforts to fino fault with this were in vain. It provided progressive stopping power and vet would not lock up easily.

Both brakes were given an extensive testing at speed and on hills. There was never any deterioration in their effectiveness throughout the period of the test. Weather conditions were a little unkind when the bike was taken out for testing. Temperatures were low and there was snow and ice on seme roads covered. The bike handled precisely on some really treacherous surfaces. The steering was superb and it could be laid over on smooth surfaces with such precision that the footrest mounts could be worn away without provoking disaster. The only criticism which could be made concerns a slight loss of ri-

gidity in the frame, undoubtedly a direct result of the new rubber mountings of the engine, in comparison with the RD3SO. On very b—apy surfaces, this induces a vague feel to the otherwise splendid handling. Some might find the softer action in the front telescopic forks — the Yamaha is inclined to

nosedive a little under braking — hard to get used to but this probably has a beneficial effect on the over-ail handling. The exterior of the twin two-stroke engine is very similar in appearance to that of the RD3SO but the internal changes have vastly improved the amount of useabie power. Yamaha now claims 40 brake horsepower at 7000 r.p.m. and a maximum torque of 3.9 kg-m at 6000 r.p.m. And much of this is available at speeds much less than the peak power speeds. Bottom gear is quite high and yet it is possible to lift the front wheel well clear of the ground under severe acceleration. In top gear, the Yamaha has plenty of power even with the engine turning over at less than 4000 r.p.m. But winding the motor up to 7000 r.p.m. or more through the gears provides some of the most exhilarating motor-cycling imaginable.

The character of the machine is such that it invites hard riding. And yet the fuel consumption is relatively good in comparison with similar twostrikes. An average of

about 44 miles per gallon can be expected, rising to more than 50 with careful riding. This is slightly better than the smaller and lighter RD3SO.

A major talking point will be the cast alloy wheels. These are probably a concession to fashion rather than anything else. They are optional at the factory but in New Zealand only the cast wheels will be imported. They have no noticeable effect on the handling, although they are slightly heavier than the wire spoke equivalent. They do have the advantage of being maintenance free. The Yamaha retails in New Zealand for $1798. ’PMificatiun* of th* RD4OO Yamaha are:— Maximum speed, 160 km/h; maximum horsepower, 40 at 7000 r.p.m.; maximum torque, 3.9kg/m at 6500 r.p.m.; engine, two-stroke torque induction, reed valve twin; displacement, 398 cu. cm; bore and stroke, 64 x 62mm; compression ratio, 6.2 to 1; lubrication, automatic; starting, kick; transmission, six-speed; minimum braking distance, 14 metres at 50km/h; climbing ability, 28deg; over-all length, 201.5 cm; over-all width. 83cm; over-all height, 109 cm; wheelbase. 131.5 cm; minimum ground clearance, 15.5 cm; weight (dry), 155 kg; fuel tank capacity, 16.5 litres; oil tank capacity, 1.8 litres; tyres, 3.25518-4 PR at front and 3.50518-4 PR at rear.