Bear in mind this book won’t have carb info relating to karting, nor exhaust.
It is 1992-97 which gives the info you need for the 6 speed gearbox.
The 1999 Karting CR125 is a mix of early bottom end (6-speed), ’99 cyl, head, and ignition. (Except in orgs that allow use of the 2001 cyl & head)
You could also order a 1999 manual for an extra 50 bucks, but it’s not really necessary.
If above link doesn’t work.