Let's talk about the airbox first!

Besides fuel, your bike needs air. Lots of it! And your bike needs the air clean, hence the airfilter.

You want an optimal flow of air towards your carburators without restrictions. Your filter is actually a restriction too...


So here are some mods!

Clean air mod (remove the KCA)

Under your airbox you will find an air suction valve which allows fresh air to flow into the exhaust ports.

Air that has passed the valve is prevented from returning.

Fair enough, but what is this shitty valve doing on my bike?

This valve is a part of the Kawasaki Clean Air System (KCA). This system helps the exhaust gases to burn more completely.

When leftover fuel is released into the exhaust system, it is still hot enough to burn. The KCA System allows extra air into the exhaust system so that the fuel residue can continue to burn.

This continued burning action tends to burn up a great deal of the normally unburned gases, as well as changing a  portion of the carbon monoxide into carbon dioxide.

BOOOOORRRRING!!!!!! Can we jank it out already?

Kawasaki advices that this valve removal should be carried out only by a competent mechanic following the instructions in the Service Manual.

Yeah Yeah, hold my beer!


A good thing about this mod is that you don't have to take a shit before starting...

This will be done in a couple of minutes!

  • Remove your gastank
  • Remove the airbox

Should look like this now:

  • Remove the valve
  • Connect the 2 reed plate hoses together or use some block off plates
  • Connect the hose from the carb float bowls directly to the front of the airbox to equalize the pressure between the airbox and the carbs
  • Blank off the other hole in the airbox!!!

Now you've got something like this:

This one goes to the front of your airbox

Because of this valve, there are some huge main jets in your carburators.

Now that your removed this valve, your bike will struggle a bit at high RPM's because it gets to much fuel!

To much fuel or not enough air?

I like how you think! You can put in smaller main jets or.... just allow more air in your carbs.

Race airfilter

Right, we need more fresh air into our carbs!

We can just get rid of the filter and maximize our airflow, but we will get a lot of dirt in our engine. We don't want that.

That's what a race filter can offer for us. More airflow but it keeps the dirt out.

Good filters are the K&N and BMC


There were some issues with the K&N on the ZXR model.

K&N doesn't sell this filter anymore because it gave less HP instead of more.

The filters for the P model are still available .

We use both filters without any problems or loss of HP


Carbon intakes

We got some carbon intakes on our bikes.

The OEM intakes have resonators so the carbon ones give a more straigth flow to your airbox

And the carbon ones saves you some weight as well.

Race airbox with FCR carbs

You can go full apeshit and get a race airbox with some FCR carbs.

A race airbox has a bigger volume because the carbs are INSIDE the airbox

If you still have 2 kidney's, you can sell one for a set of FCR carbs

It's hard to filter your air with a race airbox, keep that in mind..



TMP Summary

On our bikes, we got rid of the valve, got a race filter and some carbons intakes.

(No race airbox and FCR for us, but maybe some day... when all the stars aligne...)

These mods were some of the first, cheap and easy mods to do.

It made our bikes run more smooth and are easier to tune on the dyno.

Dyno? I tune it myself on the streets!

You just went full retard... never go full retard!

You can fiddle with the needles and jets but you will never get the perfect air/fuel ratio by slapping your dick on your carbs and guessing the right size of jets by the sound it makes.

Save yourself some time and trouble and go to an expert with a dyno to get the most HP out of your bike.

If you want to do some other engine modifications (exhaust, ignition,...) get those done before the dyno or you can start all over again.