Yamaha's new line of YZs further demonstrates the factory comittment to two-stroke development. The YZ250 and YZ125 have big changes this year, most notably the debut of the long-awaited aluminum frames. Both motors are all new with more power, and lighter weight. The YZ125 motor alone weighs four pounds less than the 2004, and with the lighter frame and swingarm, the YZ125 boasts a weight of 196 pounds (using the AMA method)!The focus of the changes to the thumpers was more useable power. The 2005 YZ450F and YZ250F have smoother power, improved ergonomics and better suspension. All YZs are sporting Yamaha's new front fork system, Renthal aluminum bars and improved plastics that reduce "bruising."