Bike for 13 year old son

Hello, I’ve read numerous threads but have not come across one that fits my sons needs. I bought him his first bike back in June an 01 TTR 125L (Big Wheel). I bought this bike to see if he would take to the sport and he has loves riding it! It’s been a great bike for him to start to learn how to ride and work on, however this lil jewel is starting to smoke and needs various other things so I’m going to sell it and get him something a little taller as he has already outgrown the seat height. The problem is WHAT to get.

The 125 has enough power for him as he is still learning but the saddle is way to small he is 13 and almost 6’0 with a 36in inseam so he has LONG legs he can almost sit flat footed on my KX450. It seems that the bigger bore bikes fit him better stock but I’m concerned with going up in CC’s, I’m assuming I could add a throttle stop or something to govern it back and slowly give him more throttle as he gets more experience. Must have a button would be great to have a backup kicker but not required. We mostly ride trails, woods/pipelines and dirt roads no future plans to MX. Can anyone tell me a good bike to get for a tall rider that is just learning or what mods could be done on a smaller bike to fit a tall rider? Unsure on what to buy.

I know there are many post on here about what to buy but I’m really scratching my head on this one your advice is appreciated.

You seem to be talking about motorbikes. This is a cycling club, as in bicycles, so unfortunately you are unlikely to receive any suitable advice here. I’d recommend asking in a motorcycle related forum.

Best wishes for your search,