I'm not dissing the movie! Note I've seen it too many times as well--otherwise how would I recognize Eric Draven's quote (to tintin, as he's got him up against the wall, right before the dagger falls and they cut to the police station). And even though there's a Ducati in the second, it still comes nowhere near the first.
I remember reading something about Japanese outlaw motorcycle gangs in the book "the Art of the Motorcycle" (published by the Guggenheim in conjuntion with the display of bikes). Apparently in Japan motorcycle gangs take 80's vintage standards and put on low clip-ons, loud pipes, and all sorts of other customizations. Still customizing, still loud, but very different than a harley with ape-hangers. I'd bet thats what this group was.