holes in airbox

[slosh13]

I've seen people with 1" holes drilled in the top of their airbox to increase air flow to the air filter. What kind of performance is gaining by doin this?

[CranMan]

If you have any exhaust mods or even a K&N this helps the engine get more air.

[redroost85]

When I drilled 5 one inch holes in my lid, I noticed much quicker throttle response. More flow=more go! :D

[mxrdr]

i have holes in my air box lid also it gives more low end and more throtle respones just like k and n says more flow = more go!:D

[Juggalo]

your better off just to remove the lid completley. when you cut the holes in there your gonna get almost as much stuff in there as with it off so you might as well take it off and have more flow and then have a fully functional lid when you need it.

[QuadTrix6]

Originally posted by Juggalo
your better off just to remove the lid completley. when you cut the holes in there your gonna get almost as much stuff in there as with it off so you might as well take it off and have more flow and then have a fully functional lid when you need it.

i have seen people install circular foam screen over the holes, has anyone heard of this. i have also seen an attatchment to a lid to make sort of a sliding doot on the airbox lid so that you can open and close it, im thinking of doing this so when i ride at higher altituded i can open the slide to let more air in..what do you guys think ?

[RuffRyder400ex]

i have holes in mine and it works great

[RuffRyder400ex]

Originally posted by redroost85
When I drilled 5 one inch holes in my lid, I noticed much quicker throttle response. More flow=more go! :D

i had holes in my old stock air box lid and it improved throttle response. i now have the alum air box w/ no lid and its even better, seems like more top end

[speedy400]

I got 6 uni hole filters for 10 bucks, they are just little foam filter kinda things. They are nice.-darren

[hondarider2006]

I drilled holes in my lid, not a lot of difference, I removed the lid completley, now theres a difference.....:D

[David]

I ordered a UNI airfilter, Outerware for the UNI (then I don't have to clean it as much). I am also getting six UNI 1'' airfilter holes.

I have stock jetting, stock pipe etc. I was wondering how many holes should I put in with out jetting at 1200 feet above sea level. I was thinking 2???

[David]

.

[Notu400ex]

Another option is to checkout:

www.ehsracing.com

You need to rejet if you open up the lid and replace the filter.

These are really nice. I bought 3 of them for each of the 400exs.

/Jon

[David]

I really like the ehs air box lid, but I would have to jet my quad. I don't what to do that, unless I got a pipe.

[Notu400ex]

rejetting a 400ex is so easy in comparison to a Raptor you can't even imagine. You can rejet it with a dynojet kit in about 30 minutes.

/Jon

[Notu400ex]

Also, I recommend taking a close look at your lid before you decide where to place the holes. Put them too far forward and they sit right on top the filter; too far back and the water kicked up from the rear tires will go right into your airbox. You are better off taking the rubber stopper out of the bottom so the water can drain out.

Also, run a bead of silicon sealant around the holes so that water can't just drain right into the box. A good 1/4" lip will keep it from being sucked in there.

In really muddy conditions, stuff some foam scraps between your fender and the airbox.

/Jon

[Notu400ex]

With any airbox mod, you will need to adjust the air mixture screw too - about 1/4 to 1/2 turn to maximize performance.

/Jon

[honda270ex]

Originally posted by speedy400
I got 6 uni hole filters for 10 bucks, they are just little foam filter kinda things. They are nice.-darren

10 BUCKS! :eek2: :eek: I got 6 of them for 3 bucks at JL products on the internet . THey work great and keep everything out of my airbox

[hondarider2006]

I just drilled some holes in my lid. When its winter I leave them open, and when its dry in summer. In the spring I just use some duck tape and cover them up so my box stays dry. I'll get some pic's soon and send them in. I didn't really notice anything with the holes, just lets my engine breath better I guess...

[David]

Tell me if you think it would work.

I ordered a UNI airfilter, Outerware for the UNI. I don't have any jetting, pipe, etc, and i'm at 1200 feet above sea level. I really don't want to jet my quad. I ride trails with mud and water, also I play at the sand pits.

If I were to take my airbox lid and turn it around so its backwards (it does fit). Then put 1 or 2 UNI airbox holes in the part that is pretty much vertical. Would this help for turbulance??? I think it would be hard to get water in by the carb.

[RIDER11X]

Originally posted by Notu400ex
Also, I recommend taking a close look at your lid before you decide where to place the holes. Put them too far forward and they sit right on top the filter; too far back and the water kicked up from the rear tires will go right into your airbox.

/Jon

I figured it would work better with holes drilled into the rear of the airbox lid so any water can fall behind the filter and not on top of it. JMO:ermm:

[JD400exrider]

If you ride in dusty conditioins those little 1" filters will become clogged in no time. ;) They will work OK if not real dusty. Here in CA it is a dusty Mo Fo right now. I am running the EHS lid with a Uni . Just bought some of those filter skins to put over the Uni for real dusty conditions. Can take them off and put another on half way through the day. I did notice last ride the UNI did let a little dust in.

Who ever said the outerwear cover on the EHS lid is water resistant is BS

[RIDER11X]

Originally posted by JD400exrider

Who ever said the outerwear cover on the EHS lid is water resistant is BS
Really? I wondered about that!

[Notu400ex]

I didn't say it but...

the EHS lid is water resistant as long as it is new and your bike isn't running.

/Jon

[ryanh250ex]

why does everybody complain so much about jetting?

i mean, yeah, it can be a pain with certain quads to take off all this stuff (plastics, etc.) but after you do it the first time IT'S SO EASY!!!

not even a week ago i took apart my 250ex to be rejetted. since i am not the quickest mechanic on this side of the Mississippi ( :) ) and this was my first time doing this (and i had alot of trouble with the jet needle retainer and getting it in and out), it DID take me 4+ hours to do, but none of it was insanely hard.....i simply followed a few simple directions and looked at the diagram in the 250ex service manual and a little while later i was putting stuff back together and i was done.

if i had to re-jet it again tomorrow, it would probably take me no longer than 15 to 30 minutes. all you have to do (at least on mine) is.......

1. take off the side panels (might not be necessary, but i did it for easier access to the bottom of the carb when i had to unscrew the float chamber).

2.take off the airbox (easy, just pull off the plastic tabs and then loosen the screws that keep the airbox mounted to the carb and the snorkel, and forget the tube that runs from the motor to the airbox)

3.take off the carb top. with that out, the throttle valve and spring will also be out

4. unscrew the two bolts that hold the carb to the intake manifold (i believe that's what it's called)

5. unscrew the float chamber (the entire bottom of the carb)....there is 3 screws holding the carb together all facing downward (meaning you have to point a phillips screwdriver upwards to get to them)....simply take out all of them and the entire bottom half of the carb falls out.....make sure your gas is off and you drain the gas out of the carb beforehand, or else you have gas spilling all over like i did (i forgot to drain the gas)

5. flip the carb upside down and there you have your jets.


this is very easy. if I can do it, anyone can.

[the yella yeti]

I ran mine for a while with the lid on and a pipe.
It ran pretty good.
Then I ran it with the lid off, and it made a significant difference. Way more power than just a pipe.
Then I had a problem with a bunch of dirt collecting in the bottom of the airbox, so I cut the whole airbox off.
It runs like a champ.
The filter doesn't get any dirtier than with just the lid off either.

[cals400ex]

jetting a 400ex is quicker than that. 3 minutes max. all you need to do is unskrew the bolt on the bottom of the carb with a 17mm wrench (make sure you turn your gas off. also, you might spill a little gas from what was sitting in the bottom of the carb). then unskrew the main jet in the bottom of the carb with a 6mm socket. then put the new jet in and put the 17mm bolt back on. your done.

[White_Knuckles]

Originally posted by hondarider2006
I just drilled some holes in my lid. When its winter I leave them open, and when its dry in summer. In the spring I just use some duck tape and cover them up so my box stays dry. I'll get some pic's soon and send them in. I didn't really notice anything with the holes, just lets my engine breath better I guess...

Increasing the airflow without a rejet is pointless and if anything may lean out the overall fuel to air ratio. Check your plug for lean symptoms and bump the main jet up 1 size, then you may notice something. ;)