My son has an all stock 60 and talk about power band!
This bike flies. He is 8 and loves the power when he wants it.
If your son has never been on an MX bike, be carefull, the 60 realy has the power!
When I was lookin, I looked at the KX60, KX65 or the KTM65(heard bad things about the KTM). Thats pretty much it in that size MX bike.
I came across a great deal on a bairly used 99' model so thats what I went with.
We ride tracks and trails, he does not stay in the power band and it has yet to fowl a single plug(32:1 Yamalube on pump 92 octain)
The only differences(besides price) in the bike that I could tell is the suspension and the brakes. Theres not much difference in the motor. Ok, 5 cc's, not much huh?
The 65 has disc brakes and the suspension is set up like a larger KX, just on a smaller scale. Plus I THINK the 65 may be an inch taller, stock.
I would however recommend trying to find a used one, after all, how long do the kids really stay on the little bikes?
I am not at all disapionted in the 60, and neather is my son.
Let us know what ya decide.