Hi all, I'm new to the forum and am thinking about purchasing a kx 100 for my son. He's 13 and is about 5 ft tall and weighs about 100 lbs. He's been riding bikes in the desert since age 5 and currently has a CRF 100. For years I've been promising to take him to the track and I feel it's probably time to upgrade.

Here's my dilemma. I'm not rich and can't go get a new kx 100. So I've been checking on Craigslist for used ones and there are a bunch of older ones around. I've talked to a couple of know it all's and it's been brought up that prior to 2014 the kx 100's have a bunch of issues. Is this true? Also does a 2004 or 2006 for example have adequate suspension for the track or is a 2014 gonna blow those years away? Last question is, if we're going to ride in the mountains (sea level to 6000ft will it run ok or will it have to be rejetted? I seem to remember my old two strokes being touchy when it comes to altitude.

Thanks in advance for any advice,