Reports out of Japan today (January 15 U.S. time, January 16 Japan time) indicate that both Yamaha and Honda are already testing four-stroke GP bikes in preparation for the 2002 racing season, when 990cc four-strokes will compete with 500cc two-strokes in the Grand Prix World Championship. While a two-stroke Yamaha YZR500 makes about 190 horsepower, the new four-stroke Yamaha already makes over 230 horsepower and has a 10 kph (6.2 mph) advantage in top speed on Yamaha’s private test course, according to racing sources in Iwata, Japan. The four-stroke’s lap times have not yet equaled those of the YZR500. The new Yamaha is thought to be a V3, although the sources would not admit to the engine configuration. If it is a V3 with round pistons, it would have to race with a minimum weight of 135 kilograms, or 5 kilograms more than the minimum weight for a YZR500 in 2002. A V3 with oval pistons will have to meet a minimum weight of 145 kilograms. Meanwhile, Honda has been testing both V5 and V3 four-stroke racebikes in Japan and plans to announce the configuration it will use in 2002 at a press conference to be held January 29. Competing engineering teams built the machines, an approach used before by Honda to determine the best configuration for a given application. Honda and Yamaha’s initial testing contributed to Bridgestone’s decision to enter the Grand Prix World Championship in 2002. Initial tests have shown both companies’ new four-strokes to be very hard on existing tires made by Dunlop and Michelin. Bridgestone recently contracted Erv Kanemoto’s Kanemoto Racing to test tires on a Honda NSR500 during 2001, in preparation for the 2002 racing season, although no official announcement has been made yet.
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