Kawasaki Sportsbike Riders Club - Australia - Online Forum

I just pulled the air filter out to check it, as everything else on my bike seemed a bit off since i got it. The filter turned out to be almost new, but as i was removing the top i noticied that it was not sitting on properly. On reassembly i made sure everything went back on as it should, took the bike for a test ride. The bike now sounds really different, as the revs get higher the bike sounds "beefer" as opposed to getting higher pitch. Is this normal?

Beefer/Deeper I guess that what you mean,should be ok
as long its not at slower speed.
Just make sure your accelaration is not suffering from it.

I cleaned the inside(box) each time after a long ride,and the actual filter too,or I would replace the filter if it was too dirty.(very thin layer of foam did the trick)

Rip the airbox and the filter out and throw it down the street, throw on 2 pod filters and get two new Kawasaki next size up jets for your carbies and then your'll notice a difference.
Buddy of mine has just done his and he recons a third more power.
Just gotta get his cams done and open up the exhaust system some how

I had the opposite problem. Bike sounded nice ran well. I noticed one day that the airbox was not attatched to the carbs ie the boods had come off. I followed by attatching the air box to the carbs as i had previously had 0 filtration (not good). After that lost lots of (nice) noise and a significant (seat of the pants significant) amount of power.

So check that you have attatched the air box to the carbs when you reinstalled it.

my GPX250 does the same thing, the lid sits up a bit making a crack.

it seems to run great though and sounds better, and i checked the plugs, which arent showing any signs of leaning out so it SHOULD be fine *well on mine, im not sure how much yours is leaning out but it shouldnt be much at all.


and to the comment about pod filters, im going to try that, but ill have to replace the airbox when it comes to getting a pinkslip i believe cause it carries some emissions vacuum lines... i THINK ... i made the same mistake on the old toyota and it got rejected.

Damon ZX9R wrote:Rip the airbox and the filter out and throw it down the street, throw on 2 pod filters and get two new Kawasaki next size up jets for your carbies and then your'll notice a difference.
Buddy of mine has just done his and he recons a third more power.
Just gotta get his cams done and open up the exhaust system some how

ooh yeh the ever popular seat of the pants dyno and the noise factor

Throw away the air box if you want to screw up all your bottom end performance and increase your fuel consumption

Who gives a shit about fuel economy on a 250, mate they'll run a day on a coke can full o fuel as it is.

I'm sorry if Kawasaki went to all that trouble in the design room creating the perfect air box pressure and all that, but like ya said, seat of the pants dyno does it every time........

Some people just love to meddle with shit and if they do, let em, never learn anything until you've farked up a few times.

Damon ZX9R wrote:Who gives a shit about fuel economy on a 250, mate they'll run a day on a coke can full o fuel as it is.

I'm sorry if Kawasaki went to all that trouble in the design room creating the perfect air box pressure and all that, but like ya said, seat of the pants dyno does it every time........

Some people just love to meddle with shit and if they do, let em, never learn anything until you've farked up a few times.

well it all depends on the purpose of your bike

pods are fine for topend performance , but yes airboxes are designed a way for a reason and going to the pods screws with the bottom end

want a cheap performance increase then change the gearing , makes fora whole lot more fun ride

agreed, leave the pod filters unless your turning your 250 into a trackie.

WRT_GPX wrote:and to the comment about pod filters, im going to try that, but ill have to replace the airbox when it comes to getting a pinkslip i believe cause it carries some emissions vacuum lines... i THINK ... i made the same mistake on the old toyota and it got rejected.

I wouldnt stress bout rego (in NSW at least) all they do for a pink slip is chesk you blinkers, head lights and brake lights. Just make sure you dont flog it in to the garage cause at idle it shouldnt make excessive noise that would elude to mods

i guess its deeper because the airbox is now resonaiting and the air is going in through the inlets it was designed with, as opposed any old where .

leave it stock, aside from maybe adding a K&N kit to it if you were deadly keen.

..I think the full term for it is still air box.
Look at the trouble some racers go to constructing areas around their pod filters to get rid of air turbulance.
I couldnt see it being pressurised (ER5).
The airbox (in this case) is a still/ready supply of air the size of the maximum capacity the lungs of the bike can use. Of course if there is not enough area for the air in the box to be replaced all the volume wont matter. Witness some of the restrictive covers put on airboxes in the old days to pass ADR's etc. and the performance difference once removed.
Also all the volume in the world dont matter if you lose velocity, at lower revs especially, and are unable to fill the space. Witness old singles where you could actually see the fuel/air charge pulsing outside the open bell mouth but never actually getting IN to the cylinder.
Not that pods dont work, but the airbox has more uses than a place for the oil to collect if you overfill the motor.

Enjoy it for what it is and save ya bucks for your next ride

or maybe if you still want to get rid of some of that restriction, just remove the top of the airbox and whack in a wad of good filter foam, and rejet it *assuming that the removal of the lid is a pretty big change*...


however with the lid removed you will probably still destroy the resonant workings of the airbox... i cant remember what theyre called but its a big thing with designing custom plenums... something waves.... *shrugs*