Harley-Davidson appears to be just a day away from unveiling an electric motorcycle, and it's teasing the new bike on YouTube. In a video, a (relatively) quiet motorcycle whizzes down a highway, letting out a sharp, almost sci-fi sound that you certainly don't hear from noisy gas vehicles. That it's an electric cycle is all speculation for now, but there's some reason beyond the video to suspect that this is in fact what's coming. Fueling the suspicion are spy shots published from the set of the next Avengers film that show a stunt double riding an electric bike from Harley-Davidson, which auto publications seem to think looks street legal and surprisingly realistic for a supposed prop.