Kawasaki and Honda have announced new 2013 model motocross machines, and the flagship of each brand, the Kawasaki KX 450F and the Honda CRF450R, each receive a new Kayaba, pneumatic front fork. The photo below is from Honda, and it illustrates the design of the new fork versus the prior Honda version. Notably missing is the heavy fork spring, and both Kawasaki and Honda claim the new fork is approximately 1.7 pounds lighter than the previous model. The new fork on each model is supposed to be easier to tune, and offer less friction for a smoother travel. This contributes to overall weight losses for both bikes for 2013.
Both the Honda and the Kawasaki 450s received engine changes, with the Honda getting an all new frame, as well. Revisions were made to the Kawasaki KX250F and the Honda CRF250R, as well, although they do not receive the air fork. Take a look at the Honda and Kawasaki websites for additional details and specifications.