jake's big airbox modification -...

Jake's Big Airbox Modification

Captain Jake, the Mel Bay of MotorcycleModification presents:

FREE YOUR AIRBOX!What follows is documentation and photographs ofthe airbox modification on a 2001 Kawasaki W650.The intention is to clear away an obstruction in thebreathing path. This is also known as the "Firewall

Mod". Note: The work is only performed on theright side airbox.

Use this information at your own risk. Thismodification may violate your warranty. Most of this

is gathered from various sources from the WRidersGroup especially Jon Haddock, cheers Jon!

This information is provided in the simplest, clearest way I can, with lots of pictures, because that's theway it works for me. If a picture isn't clear enough for you, click on it and you'll get a MUCH largerpicture with better resolution. I strongly recommend looking over this entire document before you

attempt this modification. There are things pictured here that I wish I knew about before I ran into them. Ihave one request: If you use this information to modify your airbox, please email me and let me know if

this helped you.

When working on anything mechanical, Ikeep a big box of powdered latex gloveshandy. At the end of the job you can justthrow them away, no hand-washingnecessary. Or in this case, I could takethem off, use my camera, then put a freshpair on. Or, as I was working I neededbare fingers, so I took the gloves off, thenwhen I needed to take a picture, I couldput on one glove and use the camerawithout getting it greasy. They're availableat many warehouse stores.

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First step, remove the seat. On the left sideof the bike there is a keyhole, use yourignition key here and the seat will click.Lift from the back of the seat and slide it

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Captain Jake's Big W650 file:///M:/00w650/captain Jack/captain jack/1Captain Jake's Big W650.htm

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backwards slightly, it will lift right off. Ihave a custom seat, so your seat may lookdifferent but the keyhole is in the sameplace. Place the seat somewhere safewhere you won't kick it. Don't place it onconcrete. That would pinch the seatmaterial between hard concrete and thehard edge of the seatpan.

Next you remove the sidecover. Goaround to the right side of the bike. Thereare three screws that secure this to thebike. The first two are on the side and areindicated by the two red arrows. Irecommend using a large head screwdriverto avoid damaging these screws.

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The third screw is accessed in theunderseat area. It is the exactly same typeof dark screw you just removed and isindicated here by the red arrow. Remove itand the sidecover can be wiggled and slidout. This part is largely cosmetic and canbe scratched easily in the workshopenvironment so put it away somewheresafe with its three screws. Keep the screwswith it or just chuck the screws under theworkbench right now, which is wherethey'll end up if you don't put themsomewhere safe right away when youremove them.

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I'll be using the same picture a couple oftimes, there are many things to do here.

Unclip the wire connector at the top,highlighted with the purple arrow, justmakes it easier if you move the wire thatgoes to the left out of the way.

Warning, the part outlined in blue is the airfilter and is the reusable type so usuallycontains filter oil. You are wearingappropriate clothing, right?

The green arrows indicate a circular springthat goes around the carburettor air horn.Just roll it out of its groove towards theback of the bike.

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The yellow number 1 indicates a smalltube underneath the airbox (the big greything that occupies the majority of thepicture). You can't see the tube in thispicture. There is a small wire clip on thetube. Squeeze the ends of the clip togetherand pull it down the tube. You may be ableto remove the tube at this point.

The yellow number 2 indicates a largertube. Squeeze the goldish clip and slide itdown the tube. You may be able to pull thetube off at this point. If you can't, youshould be able to as you move the airboxout of its place. There are detailed picturesof the tubes below.

6

Remove the three screws indicated by thered arrows. The top one and bottom oneare identical and should have little roundwashers with them. The middle screw issunken in and may require a longerscrewdriver. This is the very long screw.

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Next, remove the tiny silver bolt asindicated by the red arrow, it's under theseat area, just behind the gas tank. Onmine it was installed mind-buggeringlytight. I wrecked a couple of tools getting itto snap loose.

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Now you'll wiggle the airbox out. Thistakes some doing. It probably won't pullstraight out, so try moving up, down, leftand right. It's rides on two long posts thatrun across the bike from the right side ofthe bike to the left. Don't wiggle too far,you don't want to break the posts.

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Also watch at the top where there is a postthat the silver bolt screws into. It will snagthe wire bundle running across the top ofthe area. The thumb in this photo showswhere the post sticks up behind the wirebundle. You must also slide the rubbertube at the front off of the carburettor airhorn.

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Then there are the two tubes that attach tothe front and the bottom of the airbox.Here is the front hose. You can squeezethe goldish clip with your fingers and slideit towards the front of the bike, down thehose. As you move the box towards you,you'll be able to slide the hose off the frontof the box.

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This one is a little easier. This little draintube is on the bottom of the airbox and hasjust a tiny wireclip holding it in place. Youcan easily squeeze this little wireclip withtwo fingers and slide it down the tube.This tube should just slip down off the boxwith a light pull.

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Having disconnected the tubes, cleared therubber cone off of the carburettor andgently moved the top post under the wirebundle, you can just pull the box straightout. Be certain to pull it straight off, as it'stravelling along two long plastic posts,visible in the next picture.

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This is what the bike will look like whenyou've successfully removed the airbox.

The red arrows indicate the two postsyou're working along, and the yellowarrows show the disconnected tubes.

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On the front side of the airbox you willfind 5 screws, pointed out here by the redarrows. Remove all of them and put themin a safe place. Do not remove the screwsnor the big bolt that go UP into the bottomof the airbox. That's for draining theairbox. All of these screws are identical, sodon't worry about mixing them up. Youcan also remove the air filter at this pointand put it somewhere safe away from yourwork area, which will soon be covered inplastic shavings.

15

Turn the airbox over and remove all sevenof the screws from the backside, most ofthem indicated by the red arrows. All ofthese are identical except for two, whichare longer. They are marked in thisphotograph with the green arrows. Notethat the airbox is upside down in thisphotograph.

16

Now you'll have to pry apart the front andback halves of the airbox. Look forsomeplace along the seam that is a littleloose. I found one and was able to work apiece of scrap metal into the crack towiden it, then work it along the seam.


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The two halves have a thin strip of rubberbetween them to help seal them together,indicated by the green arrow in this photo.Don't rip it. This prying apart business canbe a pain, as it seems the box halves arealso lightly glued together. Keep at it, bepatient.

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Set the back part aside, you'll be workingon the front part. This is the front half. Thebig blue number 1 indicates the air filter.The big blue number 2 indicates the"foam-covered tube".

The yellow arrows show the air flow to theright carburettor. The air gets to the leftside carb through the holes in the backhalf of this airbox, visible in photo 16.Note the tiny little space it has to flowthrough after coming out of thefoam-covered tube. The space is small andrequires the air to make a very sharpU-turn. This is what we're going to correct.

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First, removed the foam covered tube.Place it on your desk and put pencils in it,for it will never again see the inside ofyour airbox! The wall that we're going toremove used to hold up the bottom of thefoam covered tube, indicated by greenarrows.

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Here's another look from a different angle.The entire shelf that's outlined in green iswhat we're going to remove.

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And here the operation begins. I used aDremel Multipro at 30,000 rpm and acutoff wheel. I made the initial cut acrossthe back side, holding the tool very tightlyto prevent it from running off into the rightwall.

Next I turned it 90 degrees and cut fromthe outside in. The cut from the open sideto the backside MUST be made carefully,as you're cutting alongside a screwreceiver. If you cut into this, the screw thatgoes in that hole may not grab well.

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The shelf has been cut away.

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The green arrow indicates the area thatyou must be very careful cutting near. Donot cut any closer than the green line tothis tube.

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I cut away the majority of the ribbed backwall, and the ridge that runs from top tobottom. Using the flat of the cutoff wheel Ismoothed ridges on the back down the

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best I could, then rounded off the screwreceiver tube. A word of warning - aDremel Tool running at 30,000 rpm is avery dangerous thing. It got slightly awayfrom me and cut a nice semicircular gashin my thumb. Rubber gloves will notprotect from this type of assault. I wasgoing to post a picture that I took of this asa warning, but it's not pretty. BECAREFUL.

Now the air path that was 1 inch wide isabout 4.5 inches.

Now take the top half and wash it outVERY thoroughly. I used Simple Green towash it. You MUST remove all the plasticdust that the cutting has created. If youfeel that this may not be that important,consider feeding just a half teaspoon offine plastic shavings into your carbs. Thatwould be VERY nasty in the combustionchambers. Clean it well. Then dry it well, Irecommend compressed air to ensure thewater is out of the crevices and screwholes.

Now you begin to reassemble the twohalves. Here is the rubber sealing strip thatgoes between the two parts. Mine wasglued to the flat edge of the top half, whilethe back half has a channel that runsaround the entire perimeter that the rubberstrip will drop into. Place the two partstogether and go all the way around the endpushing the rubber strip into the channelas the parts come together.

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Make one final check to ensure the rubberseal is in place all the way around, andpush the parts together. Replace all of thescrews. Don't forget the two longer screws.They go in the two holes that are visible inthe middle of this photograph. Tighten allthe screws pretty well, but not so tight thatyou strip out their holes, the receivers areonly plastic and seem to strip easily.

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Push the airbox back into place in thebike, being very careful to get the longplastic rods into the holes in the back ofthe airbox. Take your time, this is

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important. As you wiggle the airbox backinto place, you'll have to mush the rubbercone to get it around the air horn of thecarburettor. I started mine with one finger.

When you're putting the airbox back, youmay hit several points of resistance. Thatmeans it's hitting something solid. It willnot help to push harder, locate the sourceof resistance and move it out of the way,or maneuver the airbox around it. Onenoted tough part is the post on top of theairbox.

Then placing a finger on each side andpushing back towards the airbox with yourfingers, use your palm to push the airboxinto the frame of the bike. This should getthe rubber cone mostly onto the air horn.

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Here's a problem I ran into on reassembly.I found that it hangs up on the left side,where you can't get your fingers to pull itover the horn. I found that you can insert ascrewdriver where the green arrow is andpush the rubber cone over so it slips overthe far side of the air horn.

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Once you've checked to be sure the rubbercone is properly seated around the airhorn, work the circular spring back into itsgroove near the carb, then push thechrome ring back against the airbox.

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Reattach the drain tube at the bottom ofthe airbox, then squeeze the little wireclipand scoot it up so it holds the tube on thebottom of the airbox.

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Move to the front of the airbox andreattach this hose. This can take a littlewiggling, as this one's a little firmer. Ifound it necessary to pull the airboxtowards me a little bit to get the right angleto get the tube back on. Squeeze thegoldish clip with your fingers and slide itback towards the airbox to secure thehose.

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Replace these three screws indicated bythe red arrows. The top and bottom oneswill have flat washers, and the middlescrew is a very long one.

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Replace the small silver bolt on top,tightening it down firmly. This goes into ametal receiver on top of the airbox post.

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Reconnect this small wire bundle. Failureto do so may result in your motorcycleexploding when it reaches 88 mph. Ormaybe not, but it looks important, so snapit back together anyways.

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Gently put the sidecover in place, workingit over the two wire bundles at the top.Replace the chrome screw and washer onthe left side, then the dark screw andwasher at the bottom.

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You should have one big dark screw leftover. Put it here and tighten it down. Thisis under the seat, behind the gas tank.

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Retrieve your seat from its safe storageplace. Note that it has a tongue at the frontpart. Angling the front of the seat down,slide the tongue into this hole and gentlypush down on the rear of the seat. You willhear a soft click when it's back in place.Attempt to lift the back of the seat, thenthe front to be certain it's on securely.

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Your bike should now be back together.Go for a ride. Enjoy the additional power.You may find that this modification leadsto the installation of shims under theneedles....

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jake's big airbox modification -...

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