Removing the factory air box: Installing an aftermarket air filter - KawiForums - Kawasaki Motorcycle Forums
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post #1 of 192 (permalink) Old 07-10-2008, 03:55 AM Thread Starter
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Removing the factory air box: Installing an aftermarket air filter

Welp no one seems to have done a how-to on installing air pods on here for the new 250's. That and I was hunting through K&N's catalog and after some measurements found a cool little air filter that would work bitching...

You'll notice that it's an oval filter that has two openings so it covers both carburetors. In the last picture you can see the neck is tilted down so the air filter ducks down a bit and clears the frame nicely...

You can order it through any major auto parts store (Kragen, Napa, Autozone, etc.) K&N P/N "R-0990" .

As simple as this little filter is, getting the stock air box out is a PITA to put it lightly. I chronicled my way through tearing out the factory air box. I think it goes without saying that your results may vary and even though I listed this in steps, you may do it however you please. FUTHERMORE, if you are one of those ass clowns that thinks installing this is going to double your horsepower and fuel economy (Hell and that's simply by just putting the sticker on your bike alone) you're going to probably be disappointed. I was surprised after jetting and re-shimming the needles that this does have a huge increase in acceleration though! I don't have any HP numbers though, but I'm sure there was actually a good 5 hp increase (Which could be partly due to the fine tuning with jets). This is mainly a good 'mod' to allow easier carburetor tuning and to clean up a bunch of clutter out of your bike. It's also not the easiest thing to do so if you're not very mechanically inclined save your time and money on this one!

Edit: Also I learned the hard way that you NEED to re-jet before you can really run without the air box. If you're going to rip out the factory air box make sure you have a jet kit (with jet sizes 110-115 or so). Otherwise the bike will run so lean you won't be able to rev past 5k or so. (Look on the bright side, changing jets is a cinch after that damned air box is gone!)

OK... So to begin you literally have to rip everything imaginable off of your bike (I'm not kidding).

Step 1:

Open up and remove the stock air filter. The seat's going to have to go and so are the front fairings

Step 2:

You can see I've pulled the air filter, yanked the seat and lifted the gas tank. If you don't know how to remove the gas tank I can sum it up really quick, or you can read kkim's post on how to do this (How to Remove the Gas Tank). But basically make sure to disconnect the vacuum line to the fuel petcock, followed by the fuel line. Don't forget on the '08 models to disconnect the fuel level sensor as well (essentially anthing I circled in red). On the other side (I didn't show it) to disconnect either the single vent hose from the tank, or on California model tanks the 2 emissions hoses as well...

Step 3:

Everything here has to be moved (The air filter box components come out HERE). Remove the tank 'cross member' and set it aside. Also take notice how FRIGGIN BIG that box is. It literally goes from the battery (to the left of my hand) to the carburetors (In front of the two intake hoses in the picture). Wow

Step 4:

Might as well do the other side's disconnections now. The air filter box is mounted to the transmission via the screw circled in red. Remove this and let it hang there. It also has a clip to hold 2 wiring harnesses. Also circled in red is the breather which mounts to the bottom of the air filter box. Disconnect this bad boy

Step 5:

I'm not kidding when I say everything imaginable has to go. Here I'm yanking the battery and battery box. ..

Make sure to disconnect the NEGATIVE battery lead followed by the positive battery lead. It's a good habit to get into. Also as you might have guessed those rear fairings? They've got to come off.

Step 6:

To get the battery box out after you remove the top panel and leave it dangle, remove the battery AND remove the three screws holding the battery box to the frame...

There are two more screws underneath the battery pad which have to come out. I like to keep things together so I also circled in red the screws that hold the battery box down outside of the box. By keeping all these screws together in the battery box you're less likely to lose them.

Step 7:

Sigh... After you've removed the rear fairings and tail light assembly you're ready to drop the mud guard. The mud guard is only really held in by 4 screws (And the tail light assembly which should already be removed). The two screws in the side that also hold the fairings on (which have already been removed to remove those fairings, and there's a screw on each side of the bike underneath the passenger peg mounts.

It's kind of blurry, but here I removed the two screws holding one of the passenger mounts on and have removed the screw (circled in red) holding that side of the mud guard in. Pheww. It's the same thing on the other side.

Step 8:

I circled in red where the two intake hoses lead from the air box to the carburetors. I jabbed all around both hoses to break them free from their glue captors (I don't cater to their terrorism). With any luck you should be able to pull back slightly on the air box and separate the hose from the air box.

Step 9:

Here's where it starts getting hard to explain as there's a lot of yanking and cursing. The air box is comprised of two compartments. The side which lends access to the air filter element is removable from the main compartment. I shit you not there's 8 or so screws all around the air box attaching this guy in. Remove all of the screws and then check because there's probably 2-3 more. With any luck you'll get them all and the two compartments will separate.

With the mud guard dropped a bit you can finagle the air box around and with a lot of effort should be able to yank the small air box compartment up. Here I am pulling it through.


There's one wiring harness that I didn't look into what function it serves that connects on the mud flap. You need to disconnect that (otherwise you can't swing the mud flap around)...

So with a little effort and while making sure nothing is snagging you should be able to pull the mud flap out a bit and spin it. The main chamber of the air box pulls through where the mud flap goes and is FREE AT LAST. I didn't catch any pictures of this as I was pretty pissed off trying to get everything free...

Edit: Thanks TheDuck for the pics of the bike disassembled! (I can lie and say their mine as MINE is also blue)
Here's a good idea of what you have to remove to take out this box (Something to consider)

And the bike will wind up looking something LIKE...

Next up I'll show more magical happy pictures as things go back tog ether.

Last edited by VeX; 08-29-2008 at 10:24 PM. Reason: Adding a link:
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post #2 of 192 (permalink) Old 07-10-2008, 04:12 AM Thread Starter
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Everything going BACK in...

Ok so it begins:

To fill the void...

And another view...

Ohh shiny

I always over look some mundane details. Here I forgot to pick up a breather (and at 1am no one is open to sell one) for the gear case. RATHER than leave this open (yikes) I threw a cheapy inline fuel filter I had lying around. I've now ran out to Kragen and picked up one of their cheapy breathers and popped it back on the original tube (zip-tied to hold it from flopping around) and life is good. For future reference because I've been asked several times: The ID of the hose going to the airbox (for the breather) is 3/8" so any filter with a 3/8" nipple will work. I believe the nipple coming out of the crankcase is 1/2" so if you use a breather with a rubber female fitting on the end it should fit over a 1/2" pipe.

I didn't notice this until now, but while showing how wide open the area is which used to be occupied with the air filter box... My damned Firebird's wheel obscures this. Oh well. Where you see wheel is in actuality 'wide open space' yeah!


I'll try to show some pictures of the old air box in its entirety (perhaps in a couple hours, who knows). With the 're-install' for this you more or less do the tear down in reverse. Nothing required fabricating new brackets or anything, so that's a + . Any questions or what not, just shoot me a line!


Last edited by VeX; 04-12-2011 at 08:15 PM. Reason: Updated picture of breather:
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post #3 of 192 (permalink) Old 07-10-2008, 04:56 AM
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wow.. that's a lot of work to get to the airbox!
nice write up

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post #4 of 192 (permalink) Old 07-10-2008, 04:58 AM Thread Starter
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LOL I was literally at one point looking at it thinking "I wonder if I can get a sawzall in there and not knick the hell out of the frame". Before I started putting everything back It must've looked like I was running a chop shop! :P

As for fitament it fit really well! I measured everything ahead of time and matched the filter to MY measurements. K&N didn't recommend crap. :P

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post #5 of 192 (permalink) Old 07-10-2008, 05:19 AM
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Sweet deal!

I've been waiting to see some nice pics of getting to that damn thing.

San Diego 250R Ninja Rider
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post #6 of 192 (permalink) Old 07-10-2008, 05:31 AM
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Wow..that is crap loads of work. How long did it take you just to get that airbox out?
Now you need to rejet that carb..lots of trial & errors to get it run, pull them out, try one jet, put everything the bike...pull everything out, try another jet etc.. until you find the optimal yet..then the needles...etc...another reason why I like FI tunning so much
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post #7 of 192 (permalink) Old 07-10-2008, 08:05 AM
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Originally Posted by VeX View Post
... My damned Firebird's wheel obscures this. Oh well. Where you see wheel is in actuality 'wide open space' yeah!
That looks like a camaro back there

Nice write up & pics.

Did you ever think about hooking up the crank case vent to the AIS plate to help with venting of the CS(keeping vacuum on it). Sounds like a nice idea to me, Be just like the old race cars in a way
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post #8 of 192 (permalink) Old 07-10-2008, 10:37 AM
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great write up and nice pics. but i do have one question. why change the airbox?
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post #9 of 192 (permalink) Old 07-10-2008, 12:27 PM
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Originally Posted by llenta View Post
great write up and nice pics. but i do have one question. why change the airbox?
Yenta, removing the air box makes more VRRRRROOOOOM.

Viddy well, little brother. Viddy well.
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post #10 of 192 (permalink) Old 07-10-2008, 01:58 PM
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Did ya re-rejet yet?
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