Yamaha Dirt BikesAfter the Second World War, then company President Gen-ichi Kawakami decided to make use of a production line and tooling that had previously been used to produce aircraft propellors to produce what was the forerunner of the Yamaha dirt bikes produced today. The company then separated from Nippon Gakki Co. and became Yamaha Motor Company, named after its founder Torakusu Yamaha. The first motorcycle, designated YA1, rolled off the production line in 1954. The Yamaha Motor Co. moved forward from that point, introducing innovations like the first automatically mixed lube and fuel system for two strokes, dubbed somewhat imaginatively the Autolube System. The first of the Yamaha dirt bikes was the legendary DT1, this 250cc two stroke was Yamaha's first purpose built dirt bike. The bike made a huge impact on the North American off road bike scene.
Yamaha continued to break new ground with the introduction of the YZ250 in 1975, the first motocross bike to feature a single shock rear end.
The Yamaha dirt bikes range came to the fore again prominently in 1998 with the release of the YZ400F, at its time of release the only serious mid capacity four stroke motocrosser on the market. This bike set the benchmark for the four stroke revolution with all the other major manufacturers scrambling to play catch up with their own four stroke motocrossers. '08 Yamaha Dirt BikesYZ450F/YZ250FThere have been some engine changes for the 08 YZ450F, the intake ports have been changed and there are also modifications to the cam profiles to boost torque and improve throtttle response in the low to mid range. The bike has a new larger diameter titanium exhaust header with a changed taper to improve efficiency. The muffler has been modified to reduce length and weight but still meet AMA regulations. There's a new brake caliper up front, similar to the YZ250F, and a lighter brake disc to reduce unsprung weight.
The YZ250F has had changes made to the piston shape, increasing the compression ratio, and there's been revisions to the ignition and carburetion to suit. The 250F and the 450F have matte black finish crankcase covers. Both bikes again come standard with Pro Taper bars and Excel rims for 08. YZ125/YZ250 The YZ250 and YZ125 haven't received much in the way of updates this year, both bikes have a YZ250F style front brake caliper which is 220 grams lighter, a wave style front disc and new master cylinder. The fork protectors and axle bracket are both lighter as well, reducing unsprung weight and improving front suspension performance. They both come standard with titanium footpegs and Pro Taper bars.
At 190lb (86kg) dry for the 125 and 212lb (96kg) for the 250, both senior two stroke bikes are lightweight, cheap to maintain (ask anyone who has paid for a four stroke rebuild compared to a two stroke) and are great value for money. YZ85 Not a whole lot has changed on the baby of the Yamaha dirt bikes for this year. The 85 has a lightweight semi-double cradle steel frame, digital CDI ignition just like the bigger race bikes and compression and rebound adjustable forks and compression dampening adjustable rear shock.
(photos courtesy of yamaha-motor.com) Click here to check out all the specs and photo galleries for the '08 Yamaha dirt bikes. Click here to check out the '07 Yamaha motocross range Please note that to protect our younger visitors to Motocross 101, SafeSearch is turned on in these search results.
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