You can remove the baffle (spark arrester), but I don't know if you'll get any noticeable power gains. You could take it out and try it. It only has 3 bolts. If you don't like it, you can always put it back in and it problem needs the carbon cleaned off the screen anyway.i have a 400 ex could i take the baffle out to get more power
How much of a difference would that really make on a 400? Im considering possibly upgrading mine but not sure if its really worth it or not. Also is it louder? (im guessing it is but the thing only said it made a different noise, not louder one)By removing the baffle you are creating less back pressure. The less back pressure the more power. You will get a performance gain but it will be so small that you wouldn't notice without a dyno machine.
If you want to make the most out of your stock exhaust, get one of these...
Billet Power Tip for Honda 400EX / 400X ATV Exhaust: eBay Motors (item 350374981447 end time Jul-29-10 11:02:35 PDT)