First, a brief refresher for all those of you suffering from CRS like I do (PM me if you don't know what that means, I don't want to get ousted from the site):
My son is 12-years old, and about 5'3" tall. He is coming off a very modified TTR-125L. We ride the desert, the forrest, the hills and just about everywhere else except the motocross track. He has zero/zippo/nada interest in racing. I asked a lot of questions and got a lot of very good replies that convinced us to look for a KDX. I found a clean 2002 KDX 220 which I paid a little too much for, then immediately headed out for a 2-week riding trip.
Here is the KDX:

Here is the kid with his TTR (Bald Mtn Lookout)

Here is the kid standing next to his KDX on the Bodie Railroad Trail, Mono Lake in the background. Note the seat height in relation to his waist:

Here is the kid riding his KDX somewhere in Alpers Canyon

Here he is on some sandy single-track on 2S36 (Obsidian Trail)

Here he is proving that he can actually stop and remain upright:

More proof:

The kid and the rest of the family:

A better shot of what he has to do to hold the bike upright while stopped. Mrs 4Rider is in the background saying something like "what are we waiting for now?:

The only shot I don't have is of the stupid grin on the kid's face every time he takes off his helmet! He has told me about 50 times how much he likes his (capital H.I.S.) new bike.
We rodes for days and days, had no problems with the bike whatsoever. Before we left I mounted a new 756 on the rear. He wore that down pretty good, so I may be looking for a somewhat more durable tire in the hard stuff. He had a little trouble on the first day balancing the bike while kicking it over. Being a little stubborn, he didn't want my help or to concede that he needed any help whatsoever (wonder where he gets that stubborn streak?) By the second day I didn't have to help him start it, even after a tip-over. If I tried to help, I got a dirty look and a shove off for my trouble.
The only problem I can see is the limited range with the stock KDX tank (about 75 miles). I ordered an IMS desert tank that is waiting to be picked up at the parts counter. The IMS tank increases the range a little (1/2 gallon's worth, or about 15 miles), and is semi-clear so we can monitor the remaining fuel level. I plan on marking the sides of the tank to indicate the fuel level which will help.
Thanks to all of you who responded to my multitude of questions. I think every response I received was accurate. The kid kinda had his eye on a CRF-X and he has always ridden 4-stroke bikes so he was very reluctant to go with a 2-stroke, but reading your posts convinced him to give it a go. I don't think he could be happier. After the first day of riding he told me he was really glad we didn't get a CRF.
If anyone is interested in riding in the Owens Valley let me know. We've spent a lot of time there and I can recommend a lot of good trails as well as places to camp, eat and hang out.
Mark