HONDA
I make no claims to be other than a novice scooter mechanic on my best day - but I'm sold on the quality of HONDA manuals.
I bought the official HONDA service manual for my 2014 Forza NSS300 shortly after I brought home my new scooter.
A habit I picked up from owning VW's over the years. The factory manual was the only way to go. They were the size of phone books!
This HONDA manual is 1" thick, and very detailed and clear to follow - and I've seen my local Honda dealer pull out the same manual when discussing my scooter.
$43, new in 2014 - these often sell for $75 > $200 now, used.
Some highlights: clear drawings and photos, if needed the drawings show where and what to use for lubing, service schedule, fastener size & thread pitch and torques,
panel removal sequence! , troubleshooting charts and a color wiring diagram.
I've a manual for my Kymco, my Piaggio (factory service) and for my late Burgman 400. None of these come close to the HONDA service manual! The HONDA manual for my son's CB500X was exactly the same.
My only complaint for Honda - is they don't offer us but a small sample of their scooter line up!
Stig