The cooling system features an aluminum-corrugate radiator which is extremely light and exhibits excellent heat-dissipating characteristics. An automatically activated electric fan pulls air through the radiator in heavy-traffic situations. The system has an automotive-type expansion and recovery tank which makes airspace in the radiator unnecessary and virtually eliminates coolant loss on even the hottest days. A thermostatic valve mounted in the engine block provides quick warmups and stable coolant temperature. 2 YICS To increase fuel economy through more efficient combustion, the engine is equipped with the patented Yamaha Induction Control System (YICS). In this configuration, the YICS consists of a chamber linked to the intake manifold by a tube. Upon intake, the vacuum in the manifold creates a vacuum in the chamber; when the intake valve closes, the chamber draws in some air-fuel mixture. When the intake valve reopens, the mixture in the chamber shoots back out through the angled tube and into the cylinder, mixing with and swirling the main intake charge. The swirling charge is then compressed and ignited, burning more completely and producing more power than that of a conventional engine. INTAKE SYSTEM AND YICS 3 LIQUID COOLING SYSTEM Downdraft carb The induction system on this motorcycle features downdraft carburetion. The 34 mm (1. 34 in) Venturis are positioned so that the incoming air takes a virtually straight path through the carbs and the intake manifolds to the combustion chambers; intake efficiency is remarkably high. An accelerator pump is installed in the carburetor assembly to eliminate hesitation when the throttle is opened at low engine speeds...