I don't know any books on roadgoing NSRs, but I have a book about all the racing Hondas, that is very interesting.

Also a very good book about 2-stroke technic and tuning, even if I don't do any tuning, the theory behind it is fascinating. After all its about 2-strokes.

I can't give you the titles just now, as I'm 5 days away from home.
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Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom