also, concerning my 400ex. what exactly does a rev box do? does it have any noticable difference over stock? are they worth the money? someone help

 

they make a big difference on a 400ex. better timing curve and more rpm's. i've heard that for the 400ex that they are nothing more than a xr250 cdi. if you can find one under 100 bucks ,get it. it does not matter wich brand cause as far as a rev box goes they are all pretty much the same aside from maybe + - a couple hundred rpm's.