My son will soon be 13 and he is ready for a 4x4 ATV. I know the regulations state he should only be on a 90, but he is ready for something bigger. What is the smallest 4x4 ATV made?

I am looking for some suggestions on the next step up, without getting too big.

 

Artic Cat makes a 250, I think, you could always find a used older one, there were a few under 300 4x4s around like the Timberwolf 250, Suzuki Quadrunner,I think Kawasaki had a 250 or 300 out several years ago as well.
Don't feel bad about age, size is more important, he must be able to easily reach the controls and sit comfortably on the quad, I had my son go from an LT80 to a Honda Recon at age 9, he fit it great, and it could go anywhere my Wolverine 4x4 could go.

 

the wolverine 350 prior to 06 are great quads. full time four wheel drive that can be unlocked with the warn 424 winch. besides that you can probably find one for a great price.

 

a good dependable 4x4 is a honda trx 300 4x4. or again an arctic cat 250,300,366,375,400. and polaris sportsman 335 and the hawkeye 300.
i'm almost 13 and i started on a honda 250 2x4 and now i bot my own sportsman 400

 

One of the Honda Ranchers.

There is an older 350, a newer 420 that is fuel injected and water cooled, and an new 420AT with a totally unique automatic transmission and IRS.