David, that is mostly repro, and mostly only for the Chiefs (1200cc)
Jerry Greers have more parts for Sportscouts and such, of which the 640 is a derivate.
https://www.jerrygreersengineering.com/catalog.php
There are very clear diagrams on that website Rob, but will look in the manual later.
This one here should be the right one;
https://www.jerrygreersengineering.c...42&m=Spt_Scout
And ofcourse there is ofcourse Ziggy's;
http://www.ziggysmotorworks.com/inindex.htm
Cheers,
Lex