<Tr> <Th> Transmission </Th> <Td> 5 - speed </Td> </Tr> <Tr> <Th> Related </Th> <Td> WR450F, YZ450FX </Td> </Tr> <P> September 8, 2009, Yamaha introduced its all - new YZ450F with fuel injection . The engine cylinder is rearward slanted, the crank rod angle has been changed to provide a more complete combustion, the 5 - valve head is now a 4 - valve head, the gas tank is located under the seat, the exhaust pipe exits the rear of the cylinder, and the air intake is now in the front of the bike . They have a new bi-lateral frame which allows for new improved steering and the new engine components . The entire package comes together to create a bike that is mass - centralized . The bike was introduced by Yamaha Factory Motocross rider James Stewart. The top speed has been recorded at 80 mph stock . </P>

When did yamaha start fuel injection on dirt bikes