You could try ::.Yam-xt.com.:: Home Page ::.Yamaha XT660X & XT660R Website and Forum - I know there are user and workshop manuals to download there, maybe the parts catalogue as well. Free to register. Despite the title, the forum is focused on the XT660 models, not the older XTs. It's a quiet forum, so don't expect an immediate reply to any questions!

All sorts in here : MC "Black Bears"
Go and have a look around and you might find what you are looking for.