both rock....my crf450's (2) and my cr500 rock....a big 500 will never foul a plug.....my buddy has a yz490 and when my old 97 cr125 would foul a plug we would stick it in the 490 and he would run it up and down a few times.....take it back out put it in mine and away we go....for another hour or so lol......the 125 could never get jetted right