I found the KX500 to be a very torquey motorcycle, and when I borrowed one, I pretty much skipped first & second gear, and kept it in third gear. I don't recall ever getting to fourth gear. Even third would kick the front tyre into the air with throttle.
Now I've got a '92 Yamaha WR500. It's no KX500. However it certainly will start driving itself if you get tired. Any little throttle movement in the bottom three gears results in either wheelspin or wheelie, both of which are detrimental to control when on a woods trail. I've already had one instance where I accidently blipped the throttle while trying to slow down for the curve, and my GPS logger showed my speed go from 14MPH to ZERO when I slammed into the tree next to the trail. Though fun, the 500 class takes a very carefully setup and deliberate kick to start: You have to position then piston at top-dead-center, then give it a full kick down & hard. Otherwise, it'll backfire and either break off the kickstart lever, tear your shoe in half, or pitch you over the handlebars.
The thrill for the 500 is the fire road ride: I can go from a stop to 80 MPH in seven seconds. (That's the fastest I've gone so far before running out of straightaway). I've never pinned the throttle in first gear, and never even in second gear. In third gear, wide-open throttle either lofts the front tire by a foot or so, or else it spins whilst accelerating crazily.
If you are looking to just have fun in the woods, the 250 class is a much better choice. I got my 500 purely out of a sense of nostalgia. A more practical bike for me would probably have been a KDX200 or a mid-90's Yamaha WR250. If you really want a good mix of power & suspension, well, the Yamaha YZF450 is a pretty tough machine to beat. They have gobs of controllable torque down low and a much more developed suspension than any of the 500 two-strokers, save the Service Honda machines.