Katy Perry's new single drops a gift in Harley-Davidson's lap

Harleys in Hawaii has been streamed and viewed millions of times, by a demographic the motorcycle maker has had a hard time reaching

Katy Perry went for a joy ride in Hawaii and came back with a song that should have Harley-Davidson dancing.

Last month, Ms. Perry released Harleys in Hawaii,a song inspired by a tropical idyll with her fiancé, the actor Orlando Bloom. Within two weeks, it had been streamed 20 million times on Spotify, and the accompanying music video—which features the pop star as both a rider and a passenger on Harley bikes—had been watched over 12 million times.

Many brands now spend as much on product placement with social media influencers as they do on advertising. Ms. Perry is a