You cant beat a Breeze it is small enough to be safe for beginners yet big enough it wont get out grown too fast.The one we have has been a tank with very few troubles.

 

Better to go bigger, at 13 he still has some growing to do. Although you would be the best judge of his capabilities, I think he could handle a bigger bike without a problem.

 

I have a 12yr. old Autistic child that is about 110 lbs. and we bought a Predator 90 for him. It's the perfect size for a beginner rider at that age with disabilities, we think so. It's small enough to not itimidate him but large enough so he wont outgrow it for a few years. At 16 we will step him up to a Polaris trailblazer.[img]i/expressions/face-icon-small-wink.gif[/img]

 

I love the idea of you doing this for your lil' nephew...you are pretty cool. Ok.. my 7yr old has a predator 90 and it can pull my 115 pd. butt around pretty good, it does have the screw limiter that you want. If in time you feel he is ready for more you can remove the jumper which will open it up more. For a first timer i think they should have Full floor boards. Suspension is pretty good for stock. It can take what he will give it. The LT80/KFX80 are dependable quads. They look solid...but again i am no expert. Personally I say the predator 90 Only because I have one to give my own personal experience..and it has features you are looking for.

SAFETY GEAR IS THE MOST IMPORTANT! Good helmet, neck roll....and everything you can think of. Goodluck in your search