As with everything there is always going to be those that say "go for it, no problem" and those that say "don't do it because"
If you don't want to read a "I won't use one because" story stop reading now. If you are interested in my comments, keep reading
I won't use a K&N on anything after seeing first hand what the filtering ability is like on a 4WD. I will clarify that this was on a 4WD that is used in all kind of conditions including dust, mud and crap, not just on the road.
Before we fitted the K&N filter, we checked the inlet tract from the air filter box to the inlet manifold to see what it looked like dirt and crud wise. After many many kms (somewhere in the vicinity of 80,000) it was relatively clean and dust free.
We fitted the K&N after making sure the filter was treated IAW the instructions and used K&N stuff to do so.
After 5,000 kms of rough and tumble (nothing we had not done before and we checked the filter every week to ensure it never went dry) we pulled the inlet tract to have a look and see what we found. We found evidence that dust and crud had got past the filter and made it's way down the inlet tract towards the engine. Had it entered the engine - who knows we never pulled it down to check but common sense says yes it did.
For this reason it is my opinion that K&N are not designed for all conditions and I will not use one. That being said a K&N will probably do OK on the main roads where dust and crap is at a minimum.
The extra expense and stuff around of having to clean and retreat a K&N is also another reason I will not use one. true in the long run retreating will end up cheaper than buying a new paper filter each time, but do your math first to be sure you will get the benefit if this is your reason for buying a K&N
Power increase IMO was negligible. Induction noise increased giving the impression of more power but was it really better. I can't say as we never put it on a dyno to find out but IMO maybe , maybe not. A proper tune could probably have done the same thing.
Some other things.
Filters that rely on an oil type substance as the K&N (and others such as finer filter and uni filter) does as the filter medium will mess with electronics (O2 sensors) and cat converters if not retreated correctly. Even when done properly they can sometimes mess with stuff.
Fuel mapping on a GSX650F can be changed to a degree without the need for add on boxes. 2 of the most common are a
yoshie box and the
BikeTech Fi adjuster. I ahve the latter and can say it's a good tool. when doing idle adjustments if you go form full rich to full lean in one hit the engine almost stalls.
I won't use one on my bikes or in my 4WD but if you want to use one then read all you can about them and make an informed decision.
Don't just limit yourself to K&N either as there are many aftermarket filters out there.
happy trails
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. Before I clean the air filter next time around I will invest is 4 slightly longer replacement screws.
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