Breath Easy: we fit a K&N air-filter to our ZZR1400

Not much lasts in the world of motorcycling unless its pretty damn good. The fact that we can remember fitting K&N’s to our GPZ Kawa’s and GS Suzuki’s back in the ’80’s says much about the K&N product.


Picture: Kawasaki Heavy Industries

Now, as then, if you want to squeeze a few more horses from your bike, adding a K&N filter has to be one of the easiest mods to do. Bung on a less restrictive exhaust and a power commander and you can add serious extra performance as well as improving rideability.


Now you might think it a tad greedy to be trying to claw a few extra bhp from a bike that already kicks out close to 200. But extra power is just one of the benefits of a K&N filter. It just so happens that we’re working on ironing out a slight lumpiness in the fueling, so the more easy breathing K&N should help with that. We’re also attracted to the re-useable nature of the product. Not only is this cheaper in the long run, but it’s nice to know you’re doing your bit for the environment. Ahhh.

We’ll take you through the fitting of the filter before assessing the benefit, if any, in our road test. But first; why does the K&N liberate more power? The answer is that the design is less restrictive – enabling it to flow more air. Putting it very simply, the power you get out of an engine depends to a large degree on how fast you can shift combustion gases through it. The faster you can get air in and exhaust out the more power you can make. However, getting more air into the combustion chamber won’t make much difference if it hits a restriction further down the system. Which explains why replacing the exhaust is necessary to see appreciable increases in power. Nevertheless, in terms of ponies for your pound – not much delivers as well as a simple to fit and inexpensive K&N.

Yet, while a less restrictive filter is good for power, it would unusable if it did not protect the engine at the same time. After all, the least restrictive filter of all is.. well, no filter at all. Trouble is, if you take your filter out then anything passing by (dust, bugs, rain, small children) can get sucked into the engine. Not good. What’s needed is a filter that flows more air than a traditional paper filter but still traps the unwanted dust. The answer turns out to be a cotton filter (= high flow) that is oiled (= sticky) to give a lot of air but without letting grit into your engine (= clever). It comes as no surprise that this breakthrough in design came from K&N’s work developing filters from desert racing back in the late 60’s. They needed a lot of air getting into the carburetors without any sand. Cotton and oil. Simples.

1. Take off the panels…


Getting at the filter is not difficult – just take of the false front of the tank…although you need to take care not to bend the plastic too much. We also took off the side panel and the front fairing to avoid damage from dropped tools.


2. Replace old filter…


After that, you’ll need to remove the existing old paper filter. It’s found under a rubber flap, and beneath that, an alloy cover, and needs to be withdrawn gently. If it’s covered with muck and you shake it about then some of that debris may end up going down into the throttle bodies, which would not make them happy.

3. Flies, leaves and grit…


You’ll probably find all sorts of mayhem in the old paper filter……over time the obstruction to the filter media that this causes will reduce airflow proportionately, sapping power and damaging fuel economy. The one shown above is not especially bad, but about average for end of cycle.

4. Hoover Out ….



Once the old filter is safely out its worth hoovering inside the airbox just to make sure no grit or dead flies are left to get sucked into the throttles when the engine fires back up. Do it gently or you could succeed in pushing anything in there further in.

5. Unbox and fit


The new filter will come pre-oiled and with a tube of grease to apply to the edges of the filter. It’s meant to be a tight fit and the grease not only helps slide it in, it also ensures a gas-tight seal.

6. Slip the new filter in…


7. Maintenance

The new K&N will last the same as the old paper filter in use. When its ready to change though, you can re-use the K&N simply by cleaning and re-charging with the 2-stage recharger kit. The filter has a lifetime guarantee, and can last up to 50,000 miles between cleans, so you’ll never need to buy another paper one again.


8. Test ride

Once fitted, its time for a test ride. Dyno figures from other bikes suggest a 13% increase in power from the K&N, exhaust / power commander set-up, so it seems likely that we’re getting perhaps 2 or 3 extra ponies from the K&N alone.

Its not possible to say if we felt this, on a bike already this well endowed with power…it would be hard to spot. But on our 2009 bike we did notice smoother low down running, slightly quicker, ‘snappier’ throttle response and less snatching at low speeds; all of which suggests the bike is breathing easier.




This has to be one of the most cost effective performance enhancing mods you can do to any bike. It’s not going to transform your Honda Deauville into a Moto GP winner, but seen as part of a package, it can help make a useful difference to power output. It also makes sense from a maintenance point of view if you plan to keep the bike for a while and is likely to improve smoothness and low speed running. It certainly makes financial sense – just two regular filter change cycles and it’s paid for itself. We’ll be monitoring the effect of the filter on power and fuel consumption over the next year and will keep this article updated.