no airbox lid?

[Old Head]

I run my 400ex with out the airbox lid, but only because my k/n has an outerwears on it the repels water. I was wondering if anyone else removed theirs?

[zoe17]

No lid is a very,very common and cheap way to improve performance. If you use aftermarket exhaust and no lid you should be able to go up a jet size or two and really feel an improvement from stock.

[mojoe2878]

lots of people on here including my self run no lid or a lid with holes drilled in it. if you are running the 170 main jet that is in your sig for a pipe and no air box lid then that should be more than enough on the jetting.

[dunedragger]

I run no air box at all, and have had no problems whatsoever. The only thing I left on there was the two tabs that sit on the frame so it will hold up the filter.

[Toadz400]

I run mine without a lid and there is a big improvement over running a lid (and yes I do change my jetting). Right now I am running a 155 MJ with a Big Gun slip-on and it's a little lean because of the cold weather setting in.

Btw - I use a DynoJet kit that came with my 400ex, so the numbers are different from the normal jets you buy from the dealership.

[Trujeepr]

I did a HRC kit look alike about a month after I bought it, self modified, cut a 2 inch hole in the airbox lid, cut the snorkel off, drilled out the three way breather, and installed a 145 main. The CAM and endcap are not part of that MOD.

And as of this past weekend, I have an HRC endcap installed and i will change the jetting as soon as I get a chance run it, I think.

[muddy400EX]

i was thinking of running no lid when i get my exhaust and im wonderin if you guys that run with no lid ever have problems, like getting water in the box or anything. and do you have to clean the filter alot with it off. with a slip-on, k@n with outerwears, no air box lid and jetted would it make a good difference?

[Jason250ex]

from personal experience, chances are, if you get water in it, it would have gotten in whether you had the lid on or not

[Toadz400]

Originally posted by muddy400EX
i was thinking of running no lid when i get my exhaust and im wonderin if you guys that run with no lid ever have problems, like getting water in the box or anything. and do you have to clean the filter alot with it off. with a slip-on, k@n with outerwears, no air box lid and jetted would it make a good difference?

Don't get a slip-on, go for the full system now. Unless you plan on never putting money into the engine, a slip-on will do good. I have never had problems with the lid off, it doesn't need to be changed anymore than it had to be before, mainly because I'm always in front of my friends:D ;) . With the slip-on and K&N it should make a noticeable difference, you'll like it.

[Old Head]

yea the 170 main jet seems to work good , i used the threory of increasing the main jet until u get a stumble then back off 1 size. glad to see many of you run without the lid. I do shy away from hitting alot of water but the little puddles don't seem to get in there.

[atvridernc]

i am gonna take my lid off once i get a k&n and jet kit. more power for cheap=awesome

[muddy400EX]

Originally posted by Toadz400
Don't get a slip-on, go for the full system now. Unless you plan on never putting money into the engine, a slip-on will do good. I have never had problems with the lid off, it doesn't need to be changed anymore than it had to be before, mainly because I'm always in front of my friends:D ;) . With the slip-on and K&N it should make a noticeable difference, you'll like it.


trust me, i would love to get a full system but im only 15 and i can barely afford the slip-on so it will have to do. im just wanting a lil more power, better looks and a good sound. i really want a good sound cuz it sounds like a lawn mower right now.:(

[Toadz400]

Originally posted by muddy400EX
trust me, i would love to get a full system but im only 15 and i can barely afford the slip-on so it will have to do. im just wanting a lil more power, better looks and a good sound. i really want a good sound cuz it sounds like a lawn mower right now.:(

Well at least yours sounds like a lawn mower, usually when they are stock they sound like they have an eletric motor!:eek2:

I can see where you're coming from, a slip-on will do just fine. I have a Big Gun slip-on and love it, plenty of low end power and torque.

[muddy400EX]

Originally posted by Toadz400
Well at least yours sounds like a lawn mower, usually when they are stock they sound like they have an eletric motor!:eek2:

I can see where you're coming from, a slip-on will do just fine. I have a Big Gun slip-on and love it, plenty of low end power and torque.


yea, i had an rm125 with full DEP exhaust(LOUD AS HELL) and then i got the 400(stock exhaust) and i can barely hear it when im riding.lol