Air box lid

[DrewS]

I just purchased a 99 400EX and there isn't an airbox lid. Anyone know where I can purchase a stock lid?

I have seen the K&N filter lid for like $85. Anyone have anything good/bad to say about them?

[tri5ron]

does your quad have an aftermarket Exhaust?
if so is it a slip-on or full header system?
does it have a K&N, or UNI airfilter?
do you know if it has been re-jetted?

if you answered yes to these questions, and you re-install a stock lid,...
your bike probably will not get enough airflow.

many header, filter, re-jet combo's require the removal of the stock airbox lid to provide enough airflow.

if you have these mods already, and you still want a lid on your airbox, then you can either purchase a K&N lid, or make your own with astock lid and cut out the top, then put a Outerwears sheet over the cut-out.

many threads here on how to make your own.

hope this helps....
welcome to the forum,

[hornetgod13]

Like Tri5ron said, that quad is most likely jetted correctly with the lid OFF. If you slap a stock lid on it will run like dookie.

An EHS Racing Lid is another option. The sell for $80.00 for a complete set up. I've ran one now for nearly two years and have ran in dunes, rain and large mud bogs and puddles with no water intrustion inside the airbox.

http://cgi.ebay.com/ebaymotors/EHS-Racing-400ex-air-box-400-ex-airbox-Outerwears_W0QQcmdZViewItemQQ_trksidZp1638Q2em118Q 2el1247QQcategoryZ43979QQihZ010QQitemZ200111181954 QQrdZ1QQsspagenameZWD1V

A new lid can be purchased from www.bikebandit.com for $20.00 which would include the the lid, seal, and left/right lid hook springs. (side note: EHS lid did not come with seal or hook springs. I purchased them for $7.50)

A third option if you are dead set on a stock air box lid is Ebay. You can get a used lid for $5.00 to $15.00

Remember, anything you do that restricts the airflow, will have to be offset by downsizing the jetting.

[DrewS]

Wow I didn't realize such a small change in airflow would affect it so much. It does have an aftermarket muffler. No idea if it is just the muffler or if it is a full header setup. Right now the bike is a bit of a mystery to me. I am the third owner and the second owner didn't really know much about what the first owner did. I can see that it has an aftermarket muffler, K&N filter, and handlebars. I was told it has had work done to it to make it bigger than a 400. I do not know if it is a 416, 440, or something else. All I know is it seems to run fine, everything looks ok on it and I didn't pay much at all for it.

Would a filter lid, either improvised or aftermarket, mess with the jetting?

I guess the real question is will the seat be enough to keep nasties out of the air box when out riding trails? I don't plan on racing at all and I don't have paddles so riding in the dunes won't happen much if at all. The bulk of my riding will be desert and woodsy trails with a bit of riding through rivers and streams and mud play. At this point power really isn't a priority for me. I just want to have a good time on a reliable bike and having dirt, mud and water get into the airbox seems like a bad idea to me.


Also, I saw someone here mention that you could go from a 440 or 416 back to stock. Are you guys doing stroker kits or are you actually boring out the cylinder and putting a bigger piston in? You can't undo an overbore so I am confused. Maybe I just misunderstood the post I saw this in.

[hornetgod13]

Even installing a modified air box lid will resrict airflow some what. You might need to rejet.

Racers remove the lid entirely. I'm and trail and dune rider so, I prefer a little more protection, that's why I went with the EHS Racing Lid.

My 11:1 416cc (87mm) is a bored and honed stock jug. I would have to buy another cylinder/piston if I ever wanted to go back to a stock 397cc (85mm) set up.

[tri5ron]

It would also be a good idea to put a Outerwears "sock/prefilter", over your K&N filter.

and if you DO choose to put a lid on, then it should be a prefilter type lid. the one that Hornetgod posted, a K&N, or a DIY job, will all work just fine without significantly/(negativly) affecting your airflow, too much. (BUT, if it does seem to run a little fatter, you may need to re-jet it a little more).

I'm betting that it HAS been rejetted. Especially since you say that it may have been taken out to a larger displacement from the stock 400.

can you post a pic of the header pipe and muffler? we may be able to tell you if it is a full header system, or a slip-on installed onto the stock header pipe.

[DrewS]

I am keeping it at a friend's house until I can get my Bronco out of the garage and sold but I will try and get over there and take some pictures.


I guess I will just have to see what happens with the lid situation. The K&N on it right now looks pretty old so I might replace it too. Jetting is a new concept to me. I will have to do some more reading on it.


So the cylinder is removable and not a permanent part of the block? If so that is pretty cool.


I am sorry for the newb questions. I have an Honda OEM service manual on the way so I should be able to learn more about this soon. I appreciate the help.

[rcatvrider]

I would just buy the 20 dollar outerwears airbox lid and fabricate something like the ehs lid. It's a pretty simple mod if you have a scroll or jig saw and is alot cheaper than a new lid but will have added air flow.

[tri5ron]

you might want to take a look at these also...


http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&sspagename=ADME%3AB%3AEOIBSAA%3AUS%3A11&viewitem=&item=190230782152


http://cgi.ebay.com/ebaymotors/OUTERWEARS-Pre-Filter-Honda-TRX400EX-TRX-400EX-K-N_W0QQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247QQ categoryZ43979QQihZ006QQitemZ160253369117QQrdZ1QQs spagenameZWD1V

[DrewS]

I will get one of those socks to go over the filter.

I am looking at one of the Outerwears fabric airbox lids. I assume you mean get one of these to modify a stock lid. Why not just get one of these and be done with it. Is that just because the velcro mounting sucks?

[tri5ron]

I am currently waiting for one of the fabric lids to arrive on the big brown santa's sleighs, (UPS Truck).

I am probably going to use it as is.
But, if it tries to come loose, or any other thing comes up that I do not like about it, then I will do a DIY job on my stock lid.

also, if you are going to replace your K&N airfilter and get a Outerwears filter cover, you might want to look at this...

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=250263876494&ssPageName=STRK:MEWA:IT&ih=015

It might save you a couple of bucks to get them all together.

Besides it never hurts to change the sparkplug and change the oil and oilfilter immediately, when you buy a used machine. You dont know how long it's been since last changed.

It would be a good idea for you to give the bike a "Going Over" once you get it home, and you get your OEM Manual.
This is about the best excuse you can have to hang out in the garage, get to know your bike, (drink a brew or two), and get it all dialed in on all the adjustments.

no need to apoligize for the newb questions. we were all newb's at one time or another, and after all,...
That's what this forum is for
:D :D :D

now go get your bike and start messin around with it. but I must warn you....

THIS DISEASE IS IMMEDIATELY TERMINAL,
IT IS KNOWN AS --- A.A.D.S.
THERE IS NO TURNING BACK,
AND THERE IS NO CURE!!!

Welcome to the Club :huh :D :cool:

do you think the outerwear airbox cover restricts flow enough to down size on jetting?

[tri5ron]

Originally posted by FoxHondaRider
do you think the outerwear airbox cover restricts flow enough to down size on jetting?
I seriously doubt that it restricts that much airflow.

[DrewS]

Originally posted by tri5ron
I am currently waiting for one of the fabric lids to arrive on the big brown santa's sleighs, (UPS Truck).

I am probably going to use it as is.
But, if it tries to come loose, or any other thing comes up that I do not like about it, then I will do a DIY job on my stock lid.

also, if you are going to replace your K&N airfilter and get a Outerwears filter cover, you might want to look at this...

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=250263876494&ssPageName=STRK:MEWA:IT&ih=015

It might save you a couple of bucks to get them all together.

Besides it never hurts to change the sparkplug and change the oil and oilfilter immediately, when you buy a used machine. You dont know how long it's been since last changed.

It would be a good idea for you to give the bike a "Going Over" once you get it home, and you get your OEM Manual.
This is about the best excuse you can have to hang out in the garage, get to know your bike, (drink a brew or two), and get it all dialed in on all the adjustments.

no need to apoligize for the newb questions. we were all newb's at one time or another, and after all,...
That's what this forum is for
:D :D :D

now go get your bike and start messin around with it. but I must warn you....

THIS DISEASE IS IMMEDIATELY TERMINAL,
IT IS KNOWN AS --- A.A.D.S.
THERE IS NO TURNING BACK,
AND THERE IS NO CURE!!!

Welcome to the Club :huh :D :cool:

Thanks, I will have to price that stuff and do more research on the different filters available.

I am ahead of you on the preventative maintenance. I have already picked up some oil and I ordered enough oil filters and spark plugs to last me a several PMs. I am just trying to figure out the air filter thing so I can take steps to get that taken care of. I have done a few once overs on it already to make sure there wasnt anything I missed. The last time I checked I noticed a bolt missing on the engine down by the oil drain plug and I have no idea what it is. The manual should help. I won't be riding it until I get a PM done.

I am pretty good at fighting off the itch to upgrade things and I refuse to buy things at standard market price so when I want something I shop until I find an unbeatable deal. It needs tires but other than that I don't see myself doing much at all to it unless it is maintenance related.