Later KMX's certainely from 97 onwards have only one restriction. Remove the exhaust there *may* be a washer welded in it where it leaves the head. Newish ones there is a restricting rubber sat between the carb and airfilter. Also there is a chance that there is a piece of rubber inserted in the space between the carb and airfilter. If you are not happy to do this and worry about your own mechanical experience then don't do it.ДЄfter removing the washer and altering the valve you may need to re-jet the carb.

I am fairly sure the de-restricted KMX was good for 21bhp, you are doing all of this at your own risk as the extra power will put more strain on the engine and almost certainly will reduce its life expectancy. It will be logically positioned at the front of the engine on the exhaust outlet. If you have the blanked off KIPS valve then you just need to remove the cover and rotate the valve. With a flat file or maybe a hacksaw blade you should be able to remove the section of weld that holds it in place and remove the disk

IIRC you will see the washer (?) inside the exhaust header (nearest the cylinder head) and it will be mounted to the outer edge of the exhaust at at least two points. If it is restricted as I thought then first off you need to remove the exhaust.

Kawasaki kmx 125