I got my daughter a Honda 90 a few years ago. I must admit, it didn't take long for her to out grow it. Now she is 13 and I got her a Suzuki Ozark. She is about 5' 5" and weighs about 95lbs. She handles the Ozark quite well. Small quads are great for small kids but your son at his age will out grow a kid's quad quickly. By the way, my step-son (14) rides his Warrior with no problem. If your son wants something a little more sporty, take a good look at the Z250. It looks sporty and should last him a while. It has an auto clutch and shaft drive. If I were you I'd get an Ozark or the Z250.

 

I rode an ATC 110 unitl I was about 14 or so.. Great bike, enough power to do almost everything, and taught me how to use body english to get the bike where you want it to go. After that was a CR250... I wish I wouldn't have sold my CR... Oh well, somewhere in between the ATC250R surfaced too.. A great bike for a young teenager!

For your son - I would buy him an R'.. He'll love it, they are decently priced, and you'll love it too!

R's Rock.. It will also teach him about maintenance, which I think is important. Don't buy some wussy 250 four stroke - he'll outgrow that in a year. you never outgrow an R'.

If you must - a blaster would do nicely too.