'Maybe, but then you'd only have a Kawasaki.'
An H2 motor is two stroke, and so is an RG500. It's not as simple as just fitting a motor t o the frame. Most two strokes are completely different bikes to four stroke twins, both in power character istics and the way they handle - the weight distribution is usually radically different, and so are the power characteristics. I've built both types of bike, and the mindset you use is different for each type. I once saw an A7R Kawasaki fitted with a Triumph Bonneville motor. It shows a complete lack of riding experience - just imagination and delusion on the part of the builder. I mentioned on this forum the TZ350 fork yokes fitted to my Seeley. That is as far as I would ever go using two stroke technology on a Norton. If you have a look at that bike in the photo, you have something which is extremely torquey, with the motor too far back, and very quick self-steering geometry. If you tried to race it you would have to ride around the worst aspects of the designs of both types of bike. The builder has obviously never been grabbed by the throat by a bad handling piece of shit. Of course the question must be asked - why is he selling it ? Personally, one look at it is enough, I would not attempt to ride it fast, it is a crash waiting to happen.
When guys build bikes like that they put the rest of us at risk of needing an engineers' certificate for everything we build and race.
(About ten years ago I was involved with Standards Australia in writing 'Guide to Managing Risk in Motor Sport' . There are plenty of people about who would put us all into a legislative straight jacket.) Fortunately, if you showed that bike to most engineers, they would not know what they were looking at. However the engineer might be someone like Herb Becker.