OUTSTANDING POWER-TO-WEIGHT RATIO Yamaha 350 R5-F two-stroke twin packs a solid punch

Press, Volume CXI, Issue 32701, 2 September 1971, Page 10

OUTSTANDING POWER-TO-WEIGHT RATIO Yamaha 350 R5-F two-stroke twin packs a solid punch

(By

R. O. DEW)

VOT so long ago any ■ motor-cyclist wanting a reasonably light and manoeuvrable road machine with a sparkling performance would have been well satisfied with practically any Japanese 250 c.c. twowheeler. Now the Orientals, with their great foresight, are producing even more tempting packages machines which make few weight sacrifices in comparison to those in the 250 c.c. class in spite of considerably increased engine capacity.

A machine in this category is the superb Yamaha street 350 R5-F, the subject of this month’s road impression. It first appeared on New Zealand roads towards the end of last year and has been a steady seller since in spite of its price tag of $1095.

This figure puts the Yamaha among the dearest in its class in this country but for what' the machine offers in the way of performance and looks it is not too much. It weighs only 3101 b (some 250 c.c. machines are heavier) and with its 347 c.c. two-stroke twincylinder unit developing up to 36 brake horsepower is lively enough to fulfil the requirements of the most power-hungry enthusiast.

When the Yamaha first appeared on the world markets last year, the popular American motor - cycle magazine, “Cycle,” conducted extensive tests of six 350 c.c. machines. Afterwards, it announced that the R5-F was the world’s best production street 350. Its testers agreed that its superiority over other Japanese makes Was slight but they indicated that the Yamaha had “a tremendous amount going for it.” The test machine, provided by Velvin and Cresswell, Ltd, confirmed that the praises sung about the R5-F were not misplaced. Taking this conventional but well finished two-stroke on to

the roads for the first time was almost like renewing acquaintances with an old friend. The seating position was ideal, even if the seat was a little firm for long journeys, and the controls could not have been better placed.

The first thing one notices is the quietness of the motor and the exhaust note. This never rose above a low pitched, if purposeful, burble —unlike some of the earlier Yamahas which gave plenty of warning of their approach.

Around town, the machine was very tractible, its light weight and five-speed gearbox made negotiating heavy traffic a simple task. It would waffle along quite happily with the engine ticking over at 2000 revolutions per minute and stopstart riding was no problem. The engine would 1 pick up steadily from 2000 r.p.m. in top gear - but for rapid acceleration it was better to drop down one or even two ratios. In fifth, useful power started coming in at 3000 r.p.m. and built up to

its maximum 36 b.h.p. at 7000 r.p.m.

The Yamaha was blessed with so much power in relation to weight that it was wasted in built-up areas. Even outside city limits, the machine could not be fully extended. Its top speed of about 106 miles an hour is nothing remarkable by today’s standards but its acceleration is fierce.

Before twisting the throttle grip wide open in a single movement, one had to make very sure one had a good grip of the seat and handlebar. The Yamaha has "been timed over a standing quarter-mile strip at 14.675ec, clearing the measured at 87.8 miles an hour. It might well be able to do even better than this with expert preparation and ideal conditions. The test model, although not run in, certainly had a spirited feel not previously experienced in a machine of this class.

Engine revolutions were generally kept below 5000 r.p.m. because of the new condition of the unit but even with this reduced range there was power to spare. A trip over the hills to Governors Bay and return was an effortless romp. The steepest inclines might as well have not been there and the machine handled beautifully through the “twisty bits.”

It was effortless to lay the machine over and there was never any fear of it grounding a clearance of more than 6in made sure of this. On roads in poor condition, the suspension absorbed the worst jars admirably. The Cerianitvpe front forks mostly kept the front wheel firmly planted on the road surface, although under power it could be encouraged to lift.

The gearbox was a little "clunky” when the test began. Care had to be taken ta engage bottom gear and to change through neutral to second. But before the test was finished, it had freed up considerably and rapid changes could be made up and down the range without fear of a miss.

Overall, the whole machine improved the further it went, although even as it was it was quite delightful to ride.

In recent years, a number of successful racing machines have been evolved from standard road motorcycles. The Yamaha 350 is the reverse of this trend. It owes its origin to the remarkably successful Yamaha 350 c.c. production

racers, machines which outpace all in their class at world championship level, except the magnificent and much more complex works M.V. Augustas of G. Agostini.

The R5-F has made its mark on the racing circuits too. One won the 500 ex. class of a 1000 miles production race at Amaro Park, Australia, last summer. The power unit is a twin two-stroke with the conventional five-ports, delivering torque of 28ft-lbs at 6500 r.p.m. It is immaculately finished in black and polished alloy. The R5-F is well trimmed. Cables are tucked away and do not obstruct the speedometer or revolution counter. These two instruments are, incidentally, mounted on rubber and well protected. A trip meter is fitted as standard.

The ignition key is located at the top of the forks, just ahead of the steering damper, another item fitted as standard. The battery and oil tank (lubrication is automatic) are located under the seat. Everything is very well thought out. The Yamaha Motor Company has produced some outstanding motor-cycles in the last decade and the R5-F is one of the very best of them.

SPECIFICATIONS: maximum speed, 106 m.p.h.; climbing ability, 28deg.; turning radius, 90.6 in; mln. braking distance, 46ft at 31 m.p.h.; engine, two- ' stroke, five-port twin; displacement, 347 c.c.; bore and stroke, 2.52 in x 2.126 in; compression ratio, 6.9 to 1; maximum horsepower, 36 at 7000 r.p.m.; maximum torque, 28ft-lbs at 6500 r.p.m.; lubrication, automatic; starting, kick; transmission, five-speed; length. 80.3 in; width, 32.9 in; height, 42.7 in; wheelbase, 521 n: ground clearance, 6.lin; weight, 3101 b.