Donny,

I would assume you could order it directly from Yamaha Corp. I got my KN5000 Service Manual from Panansonic USA (Technics). Here is Yamaha's Service & Support Request website:
http://www.yamaha.com/ycaservice/group019/fgrop019.htm

You can also contact by telephone Yamaha service and support at:

(714) 522-9000, 8:30am to 5:00pm Pacific Time (Monday throught Friday.

Please let us know what you find out regarding the availability of Yamaha Service Manuals.

Scott