In the 80s, Yamaha developed the craziest engine in its history. The plan didn’t work out too well

Being. This is the commercial name that Yamaha used to refer to its high-performance engines during the 80s and 90s. This series of engines laid the foundation for production legends such as the first R1 and served as a testbed for experimentation with a clear goal: to finish. with Honda’s superiority.

One of the greatest stories in the engine world is precisely the development that Yamaha tried to introduce: an engine with seven valves per cylinder. Valves are elements that regulate the flow of fuel-air mixture into the engine, as well as the exit of gases resulting from combustion.

The history of the engine has led us to engines with more and more valves, although for many years the path to follow was clear: four valves per cylinder. We will make this conclusion in 2024. But 40 years ago, experiments had yet to take place.

The obvious challenge ahead is to surpass Honda

In 1979, Honda introduced its first 8-valve engine. This engine is a legend in motorsports as it marked Honda’s return to the 500cc category at the World Motorcycle Grand Prix. They did this with the NR500, which had a four-stroke block (two strokes were the norm in competition at the time), oval pistons, and an incredible eight valves per cylinder.

“Looking back, I’m not sure whether we were experimenting with advanced technology or being obsessed with stupid ideas.” Toshimitsu Yoshimura, engineer who participated in the development of the NR500 oval piston engine.

A completely crazy idea, born out of the need to continue to create more and more powerful four-stroke engines. But… where did this idea come from? Honda’s rivals at that time had a power rating close to 120 hp. Brutal power for a two-stroke engine.

Honda tells us that to achieve these figures in a four-stroke engine and with a maximum of four cylinders it was necessary to double the number of rpm they could achieve. To achieve this goal, they could think of nothing better than doubling the number of valves, from four to eight. And since they didn’t know how to place them, they changed the shape of the pistons: from round to oval. According to their calculations, they were going to create an engine that rotates at a speed of 23,000 rpm and produces 130 hp.

After endless headaches (some details fell apart in the face of such a beast), the goals were not achieved. The block barely reached 100 hp, and the first races with this engine turned out to be humiliating for the company.

As we bikers often say: Honda is Honda. By improving everything that didn’t work, they achieved the expected power figures, achieving their first victory at Suzuka in 1981. Given the complexity of the engine, the experiment remained what it was. Experiment.

Yamaha’s answer

Given the dominance that Honda was starting to show (or at least what they were showing them), Yamaha had to respond. Their solution was to switch to four-stroke engines, although their development was somewhat slower. To test whether it makes sense to increase the number of valves, an engine was developed with seven valves: four intake and three exhaust.

Unlike Honda, Yamaha came to the conclusion much faster: engines with more than five valves per cylinder. they didn’t make any sense. Beyond those five, the benefits in terms of airflow were minimal, and the brutal complexity they required completely outweighed any possible additional benefits they might have.

The new 500 cc four-stroke, 28-valve engine (four less than the Honda) produced 125 hp. and rotated at more than 20,000 rpm. This is a development that was never implemented, although it served as an experimental table.

Image | Honda, Driver Center, Rikita

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