You have to remove the magneto cover (left side of bike), get a flywheel puller and take off your flywheel. Then you have to get at the plate with 3 screws.. You can see that the plate has room to slide clockwise and counter-clockwise if you were to loosen the screws. That is how you adjust your timing. And remember, when you re-tighten the screws, make SURE they are tight, if not they will come loose and you'll be screwed... Check your woodruff key while you are in there and make sure it is not damaged. Now, I have not looked at the 00 cr125 specifically, but this is how the timing is changed on any other bike I've worked on. You will be able to advance or retard the timing more than enough.