The first time that happened to me I had just filled the tank and was preparing to leave the gas station. Scared the crap out of me when I felt that explosion just under the family jewels.

I shut down the bike and checked not just the bike but you know what

I had cracked the airbox but it was covered under warranty. A week or so later I discovered this site and was told "Never crack the throttle." It hasn't happened again in 24,000 miles and almost three years.