Well, since my kids have been riding it, I noticed this thing has a constant stumble / misfire between 20 and 30 mph. Mine has over 100 miles and over 7 hours. It is 100% out of break in mode. I rode it to confirm it. If you ride it like a beginner, keep it between 20-30 MPH, it constantly stumbles. If you go slower or faster, she runs like a top. I am not sure if it is misfiring or it is the knock sensor. It does it even after a run it hard to clean the plug and power valve. Has me stumped. The clutch is also noisy on this thing. Good thing I bough the extended warranty.