What type of bike does Johnny have? Do they still make them?
It's a Suzuki, you can actually see it written on the bike in one scene. If I were guessing, I'd say the producers felt like a Harley would be too cliche. They'd be right. Hope that helps.
Roarke's bike is a 1980 Suzuki GN400
The "trivia" section for the movie here gives the answer.