I got to spend a bit of time riding my KLX450 and my KX250 last weekend. I read somewhere that the KLX is top heavy and my god it is. Yeah the power delivery is smooth and torquey but when that thing starts to lean over ya just have to let go and step off. I just can't seem to use my body weight to straighten it out like I can the 250.
It takes a lot less body effort and just a little more throttle action to feel faster on the KX. At a minimum, I think you'd tire less quickly on the KX. It's hard to believe that the 450s are faster on an MX track given all the turns.
What is it that makes the aluminum frame bikes top heavy? The frame? The added weight of the valve gear?
Do the KX500 AF bikes have the same weight issue?