I have found older Japanese bikes, made before they became overly refined, to be a blast to ride. The early SOHC Honda CB750, and the early Yamaha XS650 standard are two of my favorites. I would own a vintage Japanese bike, except that parts for them are pretty much non existent. I kept my '79 Yamaha YZ250 for 8 years looking for parts to rebuild the seized top end, with no luck. I finally sold it as is. I was hoping to get into vintage MX with it, but that wouldn't have lasted long. From a riding perspective, my B5 reminds me a lot of the XS650, they both have about the same amount of vibration, and even a similar exhaust note, despite one being a twin and one being a single. Old Japanese bikes are plentiful, and if not for the almost total lack of parts, would be an easy and cheap way to get into vintage bikes.