Its very rare that the CDI boxes go bad. Usually a coil or stator is the bad culprit before a CDI box. Check your ohms on the stator and compare to your clymer manual. After that try and install new plug caps and double check all your grounds. There's one back by the CDI, one down by your stator, and the coil itself is grounded to the frame and has a + and - lead on it. Check the orange wire goes to + and black goes to -
It is possible that your stator is getting worn out and isn't providing enough energy to the CDI and coil to make a good spark.
You sure you have good gas? Reeds all good, no cracked reeds or one hanging open? What's your jetting and elevation/temps? You sure your flywheel hasn't slipped on the taper and your timing isn't messed up? When the piston is close to TDC one of the magnets on your flywheel should be passing the pickup coil, or at least close to it, depending on how much timing advance or retard you have.
Just for shits n giggles, give it a quick short shot of ether through your carbs while you hold the throttle open. Then kick it and see if it pops. If it does, then you might have bad gas or incorrect jetting. If it doesn't you might have timing or spark issues.
If you're running stock carbs, are you sure they are synced up? Have the choke tube installed?
Let us know what your jetting is and we can help diagnose the problem a little better. We need more details than what your compression is and that it won't start.