None of them have counter balancers.Service honda used the 2000 cr250 motors inthier 400ex frames.The 92 to 01 would probably be a better choice than the newer ones as they were case reed and have almost no bottom end not to mention the powervalves are cable actuated which always streched ,therefore noticeable performance loss is a way of life with these motors if you dont keep them adjusted.i used to have one in my blaster up until a few weeks ago.
426ex,lt250r banshee and kfx700 v force,yz250 mx bike