Why is Darth Vader on the Cover of Dirt Bike Magazine in 1977?

One thing we didn't know about Darth Vader was that he really enjoyed dirt biking. He loved it so much that he posed for the cover of Dirt Bike magazine back in October of 1977. 

I guess when Podracing went out of style Vader got his adrenaline rush from killing little Jedi kids and dirt biking on the sand dunes of Tatooine. That's how hardcore he was! Too bad George Lucas never explored that part of Vader's life.