Someone probably "pop-started" it rolling backwards down a hill. This caused the crankshaft, and entirely the whole motor, to run in the opposite direction. It obviously does not like being run like that, hence all the smoke.
That's funny sh*t. I usually just tell them it's a schwinn. I:I It's almost like you can see the mouse looking for the cheese at that point...but there is no cheese.
I've this kind of stuff so much that it doesn't even faze me anymore. If they want to make up BS to sell it, I'll make up BS to get them to lower the price.