Since the Yamaha "How to Care" manual tells you
nothing at all about the piano mechanism, you might be interested in Arthur
Reblitz's book "Piano Servicing Tuning and Rebuilding". Yamaha pianos are
technically the same as any other piano (except they use more metal and plastic
these days), so this book applies to virtually any piano, and it covers uprights
and grands. It is available from Amazon.
John Farmer
UK