Everyone knew about Sirius Black's flying motorbike. No one knew exactly how he acquired it but that only made it that much more interesting to speculate.

No one would have guessed that he picked it up in a pawn shop on an outing in muggle London with James and Lily. And very few people would guess that he spent the remainder of the summer between his sixth and seventh years building it from the ground up, without magic. Not that anyone cared. It was cool.

How Arthur Weasley came in to possession of it is a tale for another time.