CG125 cutting out

My mate has a CG125 and when it gets really hot (and the weather is hot as well), it splutters like the petrol is running out. I have no idea what that might be, so was wondering if anyone might know things I could check, or suggest he checks.

https://londonbikers.com/forums/posts/443804/cg125-br-k-overheats-and-cuts-out-when-idle

Oooo thanks nails