The world of two wheels is full of fascinating stories, such as that of what could have been the first motor in history with 7 valves per cylinder, four intake and three exhaust. A milestone that was within reach of Yamaha in the late 70s, in order to find an efficient alternative to what at that time seemed to be the Honda NR500.
Somehow this four-cylinder engine with 7 valves per cylinder became the germ of what would later become the famous 20-valve Genesis engine with which the Japanese firm equipped motorcycles as iconic as the Yamaha FZR1000Rof which we advise you to read our Old School Retrotest.
The development of the engine with 7 valves per cylinder
The idea began to take shape when the possibility of equipping the motorcycles of the time with four-stroke engines was considered, offering performance similar to that provided by two-stroke engines. With the arrival of the XS 650 in the early 70s, Yamaha took its first steps towards this goal.
However, its biggest rival in competition, Honda, was already working on a really interesting project based on a four-cylinder engine and a 32-valve cylinder head. Later, the brand would end up using it in its NR500, although not with the expected result, as we detailed in the special 45 years of Honda’s V4 engine: “The power of dreams”.
By 1977 Yamaha presented in the Tokyo Motor Show part of those investigations. Among others, the Yamaha YZF-R1 1000 (0W34), a sports car based on the TZ750 competition that featured a water-cooled 4-cylinder 90º V-cylinder engine and a 16-valve cylinder head. Its engine was the result mainly of the brand’s various investigations in the area of the intake and exhaust of the engine heads, in which they worked with prototypes with 6 and 7 valves per cylinder.
One of the purposes was its use within the motorcycle world championship. That is why these engines had a displacement of 500 cc, to be able to be used in the premier category. In the particular case of the prototype with 7 valves per cylinder, it could rotate at 20,000 rpm and delivered a power of 125 hp at 18,000 rpm. Both the YZR 1000 and the various engine prototypes created were never used.
Somehow, the brand was forced to refute the arguments of Honda and its 1979 NR500, even though Yamaha never had the intention of transferring its technological advances to the track. The result obtained with its 2T engines in competition was more than enough to keep it in the sporting spotlight.
However, his extensive research in this matter evolved until it finally became the Yamaha FZ 750 of 1985, with its engine equipped with Genesis technology with cylinders inclined at 45º and cylinder heads with 5 valves per cylinder, which undoubtedly marked a new era for Yamaha.
