Let's get one thing out of the way now: The Harley Davidson Seventy-Two is a bad-boy bike. Sure, the optional speckle-paint job can make it look like the banana seat off a three-speed Schwinn.

It’s this era that Harley-Davidson distills in its new Seventy-Two, a laid-back Sportster with sparkling metal flake paint introduced Wednesday. The vibe of this bike isn’t menacing so much as ...