Upgrade advice for noob quick

[NORTEXED]

:ohmy: My (13 almost 14 Y.O.) son has started racing MX. At present, he is doing it on Mom's XR100 (Yea, I Know), but in beginner class, he is placing midpack and moving up racing kiddoes on faster bikes that have been racing 3-4 years. I've got my bike sold (XR400 I bought to putter on) and have found a good looking KTM 125 SX I am considering for him. He's pretty tall and lanky (5'8") and I need advice on the bike. I don't want to throw him into a larger displacement bracket than he can be competetive in, (been racing 80 cc beginner), but he is really too tall even for the big wheel 85's. Somebody tell me if I'm making a mistake or not (and hopefuly quick), as I need to decide on the KTM tomorrow or loose it. Thanks from the old guy.

 

[x!TremeRider!x]

Motocross is supposed to be for fun! So even though im 5'7 I still have an 85 b/c my bros yz125 is bit too big for me. My thing is, get a bike to have fun and rip around on... much more funner then riding a bike thats too big for you and you almost **** yourself riding it everytime

 

[ignition retard]

I'm 5'8 and ride a yz125, which actually has a taller published seat height than the ktm125sx (39.3"/36.42"). I'm thinking that once he gets used to the bike he'll be fine.