“Banking institutions have banished precious metals and substituted a more fluctuating and unsafe medium; they have withdrawn capital from useful improvements and employments to nourish idleness for the few, who prefer demoralizing pursuits to labors useful to the whole; the peace of the whole is endangered by evils more easily to be deplored than remedied." by Thomas Jefferson,1810 (edited)
Air cooled KDXs were ahead of their time. Powerful, fun and reliable.
Newer bikes got better suspension and brakes. Some of the newer KDXs got steel tanks which were not ideal for offroad. They also got heavier. Best advice is to find a clean low-hour example. If you're from the PNW, that might be hard as those bikes were sought after. I'm in SoCal, and there are of good clean examples for <$1k.