bansheeboy 10 Posted May 28, 2007 All right I have a 02 400ex, the engine is stock other than a rev box. I have a new fmf powerbomb pipe and a used megamaxII muffler to put on it. I don't like how loud the muffler is but there is a weight and power difference. Currently i have the pipe on it with the stock muffler, (nice and quiet!) But i don't want to mess the engine up, do i need to re jet? If so where to start from. I was told a 160 worked good in a different ex with the exhaust I havebut I would like to know what you think. And yes it is a pain to pull the spark plug on a 400ex, especially when they are hot. Share this post Link to post Share on other sites Like what you are reading? Please help us by sharing this content.