2 stroke issue (rich? 4 stroking?)

At about 0:43, you can hear a pinging noise come on after holding wot for a while. I had a bad exhaust leak at the time of this video, and since fixing the gasket, the engine has a much deeper tone to it, and runs way better. However, it still does that strange pinging. Bike is an eton beamer matrix, has a pod filter (metal mesh one maybe?) Not sure on pilot jet (maybe stock?) has an 85 main, and stock exhaust with tied off egr exhaust tube. Barely hits 40mph, but was told with an unrestricted cdi (which this bike has), it should run near 50. Is it 4 stroking? Pre ignition? Rich up top? Lean?

Видео 2 stroke issue (rich? 4 stroking?) канала The Moped Messiah