His engines not running right it sounds like. This is a little bit how mine sounded when I was running on like no fuel at all on the way to the gas station. My guess is that all the cylinders aren't firing on his bike
@zaytv_1yt750 yeah but in this guys case he's got something more serious going on then just an empty fuel tank. I can just tell by how the exhaust sounds. It should still sound deeper and more throaty even when you're out of gas