125cc coughing and sputtering?
If it was a vacuum leak the revs would rise and fall without you touching the throttle. First thing you do is stop trolling the internet. Then you remove the spark plug and read what it is showing you. I will guess that replacing the plug will fix the problem.
Take it to the dealer. Chinese bike? See a mechanic and good luck. The bike is likely running lean meaning it is starving for fuel.
"I'm going to think about fixing whatevers up with it in the next week or so..." Why? Even Chinese bikes have warranties. If it's not running right, then it back to the dealer and get them to sort it out for you.