AK; +1 on what Noprogram wrote. You would be better off with the Honda manual rather than the Clymer or Haynes type manuals. They are too general. The Honda books come up on eBay all the time. That said, you might try your local library and pickup whatever they have to get acquainted while your proper manual is located. There are lots of general maintenance books out there too. Good background for learning. Good luck.
1991 Honda XR628R
1978 Yamaha XT500