Sunday, 19 February 2017

Yamaha YR5 (1970) Engine specification, Color, Weight

Posted By: ygshhd 21:54 Leave a Reply

Yamaha YR5

The YR5’s styling was simple and obviously road-based, in contrast to earlier dual-purpose Yamaha twins. High handlebars did little to dilute the aggressive, rev- happy image of a bike that was closely related to Yamaha’s racers.

Yamaha’s two-stroke middleweight twins were among the outstanding bikes of the 1970s, providing a combination of performance and value that made them hugely popular. Best known were the RD350 and RD400 models but it was with the earlier YR5 that the legend of Yamaha’s giant-killing 350cc two-stroke screamers began.

The initials RD stood for Race Developed, and that was very much true of the YR5 too. Yamaha had already begun to dominate 250cc grand prix racing when the YR5 was introduced in 1970. In that year Yamaha’s TD2 air-cooled twin-cylinder production racer not only took British rider Ron Gould to the world championship, but it also occupied the first seven places. Much of the same technology was used for the roadsters, which were also produced in 125, 200 and 250cc capacities.

Like its smaller siblings, as well as predecessors dating back to the YR1 of 1967, the 347cc YR5 was based around a piston-ported two- stroke twin with a 180-degree crankshaft arrangement. It breathed in through a pair of 28mm Mikuni carbs, and out through a pair of horizontal chromed pipes. The gearbox was a five-speeder, with a modern change pattern that put neutral between first and second, instead of at the bottom of the box like some rivals. Peak power was 36bhp at 7000rpm.

In contrast to the off-road-influenced styling of its predecessors, which had featured crossbar-style handlebars and high-level exhaust systems, the YR5 was very much a roadster. Although its handlebars were still high, the bike had sleek and simple styling, and was shorter, lower and lighter at 33lib (I50kg). Its frame was a twin-downtube steel structure, reinforced at the steering head and swingarm pivot with the benefit of Yamaha’s grand prix racing experience.

Noise, smoke and acceleration

That racing heritage was clear on the road, where YR5 riders required little imagination to see themselves in the saddle of a high-revving grand prix racer. The Yamaha two-stroke burbled, rattled and smoked (when cold) like a true two-stroke, albeit a sophisticated and well-behaved one. More importantly it had thrilling acceleration, revved to 8()()0rpm through the gears, cruised smoothly at an indicated 80mph (I29km/h) and reached a top speed of 95mph (I53km/h).

Handling was pretty good, thanks to the rigid frame, light weight and simple but reasonably well- controlled suspension. Cycle World described the YR5 as a quick-handling machine, with ‘little to inhibit the rider from pitching the machine aggressively through his favourite set of bends. Damping seems quite up to par, and the tyres deliver good tracking precision and traction.’ The Yamaha’s front and rear drum brakes were progressive, grab-free and with only a slight tendency to fade under repeated use.

The YR5’s blend of good looks, reliability, lively performance and competitive price quickly made it popular on both sides of the Atlantic. For the next few years Yamaha’s two-stroke twins would be hugely successful in the showrooms, just as they were on the racetrack. The old adage that 'racing improves the breed' was never more brilliantly proven.

Yamaha produced a string of outstanding sportsters as the two-stroke middleweight was updated throughout the 1970s. A notable jump came in 1973 with the first RD350 model, which featured a reed-valve induction system, six- speed gearbox, powerful disc front brake and, on a good day, a top speed of over 10Omph (161 km/h). The RD400C (below) arrived in 1976 with angular styling, improved handling and extra mid-range performance from its 398cc, 40bhp engine. Similar 250cc versions of both models provided almost as much speed for even less expense.

Specification Yamaha YR5 (1970)