Just don't park your ride, whatever displacement, out of gear next to a curb on a slope, pointed down slope while using the sidestand...
As I walked away from my bike, I heard this nasty CHUKK sound. Turned around and saw this... I had to take a pic just so I could help others not have this problem. This was years ago, but I still have a scar on my alt cover. I patched it with PC-11 two part epoxy--cheaper than a new cover...