i have just got an 03 400ex, i don,t no enough about the different pipes yet and neither do the guys in the bike shops, which pipe and filter set do all you other guys run ,im looking for out the hole and middle not to bothered about top end,and if i use a k&n power lid do i need to block off the vent pipe,with a slip on muffler and filters will i need to re jet ,its around 20d in winter and 35 in summer sorry don,t no the altitude.....cheers guys

 

i would look into sparks x-4, lrd, hmf, etc

 

I would go with a Sparks full system. I believe they had the most hp gains. You will pay$$$$ for it though.

Go with what they recommend for jetting in their instructions.

K&N filter with an Outerwear,,,and remove the airbox lid (unless you plan to go swimming).

 

I have rode only 2 400ex's one stock the other one has the air box eliminated and a DG exhaust. Sounds great but pretty loud if that is a concern of yours. And gave it great low end IMO.

 

pommydude....I cleaned up the potty language and corrected your grammer in the title. Go easy on the language. BTW, the mag shootout revealed the White Bros E series was the best exhaust for your 400ex. Are you holding onto something, it turned loose a screaming 2 clydesdale horses!
Gary

 

Just buy a good quality muffler and grind the welds out of your stock headpipe. You'll save alot and gain as well...

 

It's not even worth the trouble, keep it stock and take out the baffle or something.

 

dont listen to this guy, taking the baffle out doesn't do anything more than make the quad extremely loud and obnoxious.

 

That's basically what an aftermarket pipe does on a 400ex but it's a few hundred $$$.

 

i just made some enquires about shippin over a big gun power pack from the u.s full system ,filters and jets, what do u think of that......thanks again