Powerful. Agile, Smooth. Improved. These are a few of the words being used to describe the new 2008 Yamaha YZ450F MX bike. From the reviews being written by testers of the new YZ450F mx I am getting the impression Yamaha has done a very good job improving this monster of the berms.
Introduced in 2003 the YZ450F was a logical next step to the YZ400F and YZ426F motorcross bikes. Yamaha has been refining the big-bore thumper YZ each year and this year's bike appears to be the best so far. I've read this is the same motocross bike that factory rider Grant Langston rode when he won the AMA Motocross Championship this year. I imagine Grant's YZ had a few factory tweaks to it but not a total one off factory job. I imagine this is also basically the same bike Chad Reed is riding in the Supercross series and he is really tearing it up, winning several races so far.
The motor is basically the same as last year but with a few refinements like improved intake port shapes and improved intake and exhaust cam profiles. Yamaha did this to help with combustion efficiency and also these improvements show up in better throttle response and more torque. As if this beast needs more torque and power!
Other engine changes include closer tolerances between the piston and cylinder to reduce engine noise and a new bigger titanium exhaust header that mates up to a shorter "punched-cone" muffler. Tests on the bike have proved these engine changes have produced a much smoother power band with strong pull from bottom-end to peak RPM. No sudden power surge, just smooth power from idle to berserk. All this awesome power flows through a 5-speed transmission with decent gearing and a nice clutch feel.
The aluminum frame has been given some love also with Yamaha's tuned-flex technology. Say what?? What tuned-flex technology means is Yamaha can use different alloy castings for different parts of the YZ's frame. For example the swingarm might be a certain alloyed grade of aluminum while the triple clamp for the forks would be made of a different material. Speaking of the 450's front end the forged lower triple clamp is lighter and helps the monster YZ turn much faster and the new speed sensitive Kayaba forks have almost 12 inches of travel. They also have new transfer control valves on top of the fork springs that allow damping force to be controlled by the piston speed. This all spells---more reliable and consistent damping. Yamaha did not over look the front wheel axle and collar which are lighter.
Rear suspension changes include a new titanium spring on the shock. This lightweight spring provides less unsprung weight and contributes to better shock feel. Better traction and twelve and a half inches of travel round out the rear end changes. All these front and rear suspension changes have resulted in a motocross bike that tracks better, hooks up better, has a smoother ride and puts all that power to the ground better.
The new foot pegs have all the test riders heaping praise. They are much wider than previous foot pegs and provide improved boot grip with greater stability through the whoops and over jumps.
Price for this great new YZ450F is a tad over seven thousand dollars but you are guaranteed the ride of your life on your local MX track!