Probably more than you want to know about CDI boxes:
http://www.geocities.com/a57ngel/moto/CDI.html
modding to change the timing curve:
http://www.geocities.com/a57ngel/moto/CDI-mod.html
Lynn Edwards (a forum member here) has some schematics of Chinese CDI boxes:
http://s397.photobucket.com/albums/p...nt=5pinCDI.jpg
A "generic" 5 pin CDI (noting the value of C1 and how it relates to the above mod)
http://s397.photobucket.com/albums/p...0ccCDI6Pin.jpg
This one a 6 pin GY6 CDI (again noting the value of C1)