Ok, please don't flame me for this question. I have a completely stock 2004 400ex and want to improve it some. I am realistic, and don't need to be the fastest out there. I have seen "complete systems" advertised in magazines. Other than a pipe, what do I need? I have read about jetting and new filters...do I need this in addition to a pipe? What is the advantage of a slip-on vs. a full pipe? I am not too mechanically inclined, so you might have to explain it layman's terms.

I don't want anything particularly loud since I live in California. Price is an issue, so please don't direct me to something that costs $10,000 to purchase.

 

go fullpipe and you will have to rejet and get a good airfilter like K&n
white bro's makes a good full system
with a full pipe you let the engine breath easier less restrictions in exhaust
and when you do that you have to rejet
go here[S=]www.rockymountianatv.com[/S] they have a good
selection and prices. oh and once you start changing the bike you never stop

 

also tryhttp://www.albaaction.com/ or http://www.lrdracing.com
look around theres lots of brands to choose from

 

Not sure you really need a full system with a stock motor. The stock head pipe on the 400ex is quite good and you can get a slip on for about half the price. I went with the White Bros. "e" series slip-on, a K&N with outer wear, removed the airbox lid and a 175 main jet. The difference was very noticable especially in the low and mid range. Much crisper throttle response. I can stay in 3rd when I used to have to down shift to 2nd. Total cost $280.00.

 

On my 400EX I have an FMF (http://www.fmfracing.com/) PowerBomb Header, PowerCoreIV Muffler with Quiet Core and Spark Arrestor Screen (meets Calif./AMA 96dB), UNI Foam Air Filter (http://www.unifilter.com/atv.htm), and EHS Vented Airbox Lid (http://www.ehsracing.com/). And of course, a rejet. Has proven to be a great system, though I might go with an FMF Ti-4 Muffler if I was getting it today. Take a look at the FMF Q Muffler if you really want to be stealthy.

One note: I use to run a K&N, but have gone back to a foam air filter, for some added security. The UNI foam filter has a different wire insert than the stock one, and flows almost as much air as a K&N. Venting the airbox lid is a must!