Maybe one day I'll be the guy who's answering all the new-b questions but until then I'm playing the role, I want to get a slip on for my 05 400 ex and the dealership told me to keep the engine reliable and its longevity just to put a slip on and k&n airfilter and rejet it, another dealer told me to get the whole pipe or nothing would be gained (money in his pocket) I've used the search but their old questions so I ask....a good slip on with power, mid range, (thinking of a fmf titanium mid but will it fit on the stock header??? and also should I add to my sprocket size or stay the same............any advice would be appriciated................thanks, B

 

Indeed money in his pocket, but it will help. Granted, the 400ex stock header is decent, it is semi-restrictive. Also, order it online, don't pay dealer mark ups. HMF are popular choices.

 

I love it over 40 people have read this and one person replied to help with a suggestion, boy If I posted something like can my cat beat my neighbors cat then shoot the post would never die. Come on guys look I just want a slip on and K&n air filter because i dont want to go into the motor because its so new, so I'm asking do you guys know if these hmf slip ons will fit on to my stock header bla bla freak'n bla?????

 

I'd go with the White Bro's pipes. i had them on my old 440 and it was great. granted didn't do as much as a full system does. the only thing you have to watch out for is that you can NOT buy just the header from White bro's down the road if you decide to. i found that out the hard way.

 

Maybe those 40 people knew they were going to tell you something you didn't want to hear????
My first advice is DON'T GO WITH THE K&N. Get a ProDesign adapter and foam (UNI) filter.
Second, I never tear into my engines either. I am willing to sacrifice a lot of performance in order to maintin reliability. I never do just a slip on. I always go with a full system. I'm partial to the FMF Factory 4.

 

depending on what kind of riding you do or plan on. there are some good slip on units out there if you are planning on doing some motormods in the future than you may want to go with a full system.

 

Well thanks for replying guys, So then can i get a whole pipe and airfilter and not have to go into my motor or not? I guess I want the most preformance without going into the motor yet.

 

NO you dont have to go into the motor, but you will need to rejet you carburator

 

I put an HMF slip on on mine. I don't plan on getting any deaper into mine until it has to be done, thats why I didn't bother to get a full system. I have heard that it really doesn't help much until you start getting big bores and strokers and such. My Hmf is loud, I mean WOW LOUD!!! I got a good deal on it, but I would sure like to have a quite core for it. If you just change the pipe, and filter, and either take the airbox lid off or drill holes in it, all you'll need to do is rejet it.
Depending on your riding style, I would sujest droping a tooth on the front sprocket. Unless your riding wide open in high gear bouncing off the rev limiter (like most of the guys on these forums, you know the ones always asking about top speed) you'll not notice the loss of speed. BUT you will sure notice the gain in take off and low end.
I really have liked the mods I've done to mine, and I believe that it should be as reliable as stock. It won't beat 450's, but then again, I don't care. I like it.

GOOD LUCK!!