When my chain broke, it got lodged in the bolts that hold the sprocket to the cush, wedging itself against the swing arm, and locked the rear at about 50 mph. I kept the bike up, but it was all over the road. I wasn't on the gas, just cruising at about 50 or so, and it let go. It took me and 2 other guys on the side of the road to get the chain out so I could roll the bike around.
This was the stock chain with about 12K miles on it.
