I've never seen a bad CDI, but problems when hot do indicate electrical issues. Check the regulator. All those quads have bad ones or will eventually. Just pop it off and look at the back. Another way to test it is to turn the lights on and see if it runs better. Put a big electrical load on it to lower the voltage. The problem is the voltage runs up to 16-18 volts and causes the CDI not to function. Turning the lights on reduces the voltage and restores CDI functionality.
If it is the regulator, don't buy another stock one. Contact Ricks Electronics and order something bigger.
That engine doesn't care about compression leaks because the stroke is longer than the bore. The only symptom it would produce is hard starting when cold.
I have the kingquad 300 and have put the 250 CDI on because it has a higher rev limit.
