400 EX FMF exhaust set up

bansheeboy · 05-28-2007, 12:32 AM

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.

*mywifeknowseverythin* · 06-03-2007, 01:28 PM

Most of the time when you Put any Aftermarket pipe and Silencer on you will have to Re-Jet...Normaly they come with a new needle and Jet kit...Yours didnt??? Anyway,,,,The only real way to know what is going on in your motor is to do a Plug Chop...Read the plug and Adjust from there.....Hope that helped....

*mywifeknowseverythin* · 06-03-2007, 01:30 PM

And another thing.....Along with the new pipe and Silencer....You may want to make some adjustments to your Air Flow Via your Airbox to get the Best Results Overall...