What bike to step up to

GasGas MC125

Very Competitive/Cost Effective

Probably can't go wrong with any of the new 125s.

Can’t go wrong with a yz125, if you’re patient you’ll find deals on them, good used parts readily available and there’s a wealth of knowledge at a place like this for them. The YZs are a tried and true workhorses

The GG is another great option if wanting to buy new.

A practice and race bike is the way to go if you can afford it.

can't go wrong with a used TM400.... they have everything- crazy power... crazy handling... and crazy pricing!

I went down this path with my oldest son. He was 14 and 125 pounds. I went the route of the YZ125 and he kind of struggled on it. He hit another growth spurt and we went to a Yamaha ride day and test rode the YZ250F. Night and day difference. He absolutely loved it. Sold the 125 and went with the 250. Now I'm in the same boat with my youngest son. He's 13 108 pounds. He is hitting his grow spurt but not putting on the weight. So, the 85 is up for sale and were going to go the 125 route. He dabbles on my oldest 250 here and there but I think the 125 is going to fit him better and last for the next 2 years minimum unless he puts on some weight and then we'll see how he does from there. It really just depends on his skill level.

125. I was 14 and about 5'8", 135 pounds when I got mine; I had no trouble at all. Your kid is a little smaller, but if he can touch the ground with both feet, he's golden. Since he is riding superminis, he'll easily adjust to the power. All he'll have to do is learn how to handle a larger chassis. Plus, I think everyone should have the experience of racing a 125; you learn lessons on that bike you can't get with any other machine. The brand is nearly irrelevant if we're talking new. KTM/Husky/GasGas/Yamaha. All are fantastic machines.
Once he has that under control, you can bump him to a 250F and it won't seem like such a change.

I hear over and over that riding a 125 is the best way to learn fundamentals, keeping momentum, line choice, being in the right gear, etc...

My son's complaint was, it was almost impossible to get a good start against the 4t bikes.
This was 6-8 years ago when he was on a yz125. How it is now, I suspect the same.
So the question is, are you giving him every advantage to win that you can?
Are you in it for results or skill building?
TM

Keep him on the 125
As mentioned the two stroke will make him a better overall racer
The start disadvantage is not enough to be the decision maker on which bike to buy
My oldest was great off the line ( 250F ) and he raced a 125 kid that was right there with him on the start . A skilled rider can get the 125 up front off the start .

I’d say just stick with a 125.

He’s a pretty ideal size for one tbh.

CR500

It depends, if u guys in for fun only and no big future plans, then go with the 125. If u guys planning to go pro one day, then don’t waist the the time on 2stroke !