Liquid Cooled Engine

Some stuff that Yamaha has to say about their Liquid Cooled Engine on the YZF-R15 engine!

Liquid-cooled
First India-made model with cooling method in the Indian market! Liquid-cooled engines provide stable performance, reduce vibrations, and offer a high quality ride.
One characteristic of YZF-R15’s new engine is that it is liquid-cooled. The engine is surrounded by a water jacket in which coolant liquid circulates to cool the engine. While this method is widely used in automobiles and large capacity motorcycles, there are very few examples of motorcycles of this class due to increased weight from components such as radiators. YZF-R15 uses a special compact and lightweight aluminum radiator and a body design that utilizes airflow for heat dissipation. This has enabled us to create a lightweight, compact body while retaining its stable performance.
The benefits of using this method include stable performance during long-distance, high-speed riding and hill climbing. A liquid-cooled engine does not need heat-dissipating fins and therefore the engine is able to deliver its best performance without being affected by temperature. Additionally, because the head and cylinder are enclosed in a water jacket, mechanical noise from the engine is reduced dramatically.
The newly developed engine delivers agile riding performance, and excellent performance on straight stretches of road as well as on winding roads. YZF-R15 also delivers excellent environmental performance. These traits are a must for an “urban supersport.” The ride is unprecedented in terms of both excitement and quality.