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Feature: The Versatility of Yamaha 4-Strokes - The Aim of the Shift to 4-Strokes

Introducing the potential Yamaha saw in 4-stroke snowmobile engines

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YAMAHA SNOWMOBILE MAGAZINE
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Pioneering: The Aim of the Shift to 4-strokes

The Aim of the Shift to 4-strokes

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Based off of the twin-cylinder GX400 motorcycle, Yamaha Motor Co., Ltd. developed its first 4-stroke engine more than three decades ago in 1979. The project proved that indeed a quieter, cleaner running (low emissions) snowmobile could be built with a 4-stroke engine, but most of the development projects ran into the same deterrent of poor acceleration performance and were eventually abandoned. In 1990, Yamaha engineers working on the development of a prototype using the FZR400, 4-cylinder 4-stroke engine found themselves unable to get the performance they wanted in the areas of drivetrain feeling and starting performance in cold weather. In 1998, when another Yamaha development team attempted to design a 4-stroke sport model, they found that the heavier 4-stroke engine spoiled the sportiness of the ride. For that reason the project was eventually abandoned before a product ever went to market.
During this period of repeated attempts and failures, there was debate among the Yamaha development teams about whether the 4-stroke engine was suited to sport models or whether it was better oriented to utility models. It all came down to the underlying belief that a 4-stroke engine basically required a larger number of parts that made it larger and heavier overall than a 2-stroke engine, which in turn had negative effects on handling and acceleration. In fact, however, that conclusion had not been reached in 1999 when the fourth major project was undertaken by Yamaha to develop a 4-stroke engine for sport models, which eventually would lead to the birth of Yamaha's first 4-stroke snowmobile, the RX-1.
You might ask why Yamaha wanted to build 4-stroke sport models in the first place. The answer would be the great potential that Yamaha envisioned in the 4-stroke engine as a power unit. Of course, that potential was not simply in the realm of sporty performance. Yamaha planners and engineers believed that the 4-stroke engine had great potential not only in terms of raw performance, but also in the areas of reliability, comfort and pleasure in use, environmental friendliness and economy. In other words, they envisioned a potential for new value in the 4-stroke as a power unit.

The idea of developing what Yamaha calls the "total performance" of a product is something that had been actively pursued while Yamaha was still the leader in 2-stroke engines, but this new challenge in the realm of 4-stroke products would give the engine an even bigger role in defining a product's appeal. This process involved giving the different components of the power unit different roles. Some would contribute to reliability and weight reduction, some would contribute to environmental performance and fuel economy, and there would be others filling a wide range of functions. In this way, Yamaha engines have come to consist of an array of highly versatile components.
Of course, assembling an engine of versatile components in itself does not ensure that it will be a good power unit. The basic requirement of a good power unit is that its essential elements, including the cylinders, connecting rods, pistons, crankshaft, etc., are all outstanding components in themselves. But, the aim of Yamaha's design engineers lies beyond that. The task Yamaha engineers set for themselves was to fine tune each of these components until they were all aligned along the same "vectors" of the particular power unit's design objectives. Only then would they achieve the kind of "total performance" that Yamaha seeks in a power unit.
Yamaha engineers call this kind of engine design the "ultimate lapping process." This process of high-precision refining of components to fit together into high-quality, purpose-specific power units has led Yamaha engineers to countless innovations, and those innovations have made Yamaha engine design an "art" and created "new value" that is unique to Yamaha products.



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