I believe it is your carb , needs a good adjustment/fine tune on it. And when adjusting a carb like that you have to take your time, it takes a few seconds sometime for the adjustments to catch up and level out.. your already running pretty fast or sounds like it in your video, before you start it turn the mix in till it bottom out then back it back out about 1-1/2 turns should be close, then start it up and tweek it from there , just remember do this in small increments and allow it to catch up before you turn it anymore , or you will miss the carbs sweet spot and have to start over. JMO
Cole