The problem with K&N filters from how I understand it is they are based on microscopic holes to allow air to flow. The oil that is saturated around the gauze acts like a magnet for dirt particles. When the dirt builds up its suppose to actually help filtration. But the fact still remains, its based on pin holes that have a direct shot into the carb. K&N filters are designed for full sized cars that have rings around the piston. Microscopic particles arent as dangerous to them as it would be to a ringless 2-stroke. Here's a post from Richard at K&N Filters:
That post is a fake and has been around for over 5 years. How do I know?
We do not make filters for mining, construction equipment or a Cummings V12.
Even if it were true, that would be kind of expected if you use a filter
suitable for a 1.6L Honda Civic on a turbo charged V12. Furthermore, when
used in strictly off road situations, a nylon prefilter is recommended.
These are to keep heavy levels of dirt from building up on the filter and
clogging it. If a filter was to clog on such a large vacuum producing
motor, dirt can literally pulled right through the filter (paper implodes).
Oil analysis is not accurate either when using oil impregnated filters.
They can skew silicate readings. Here is the low down on our filters...
Our filters are tested by an outside, independent laboratory. They have
been proven to stop at least 99% of particles on a SAE dust test. This test
uses particles as low as the 0 - 5 micron range and goes up to 20 microns.
For comparison, a paper filter also stops 99% on the same test and the OEM
minimum standard is 96%. Foam is generally the worst media with a typical
efficiency rating of 75 - 85%. To get higher ratings, the foam must be more
dense and therefore way more restrictive. The "tack" characteristic of a K&N
allows for increase filtration without loss of flow as well.
The testing procedure used is SAE J-726 using ISO Test Dust. This test is
the standard of the air filter industry. The test procedure consists of
flowing air through the filter at a constant rate (airflow rate is
determined by the application) while feeding test dust into the air stream
at a rate of 1 gram per cubic meter of air.
As the filter loads with dust the pressure drop across the filter is
increased to maintain the prescribed airflow rate. The test is continued
until the pressure drop increases 10" H2O above the initial restriction of
the clean element (in this case .78" to 10.78" H2O). At this point the test
is terminated. The dirty filter element is then weighed. This weight is
compared to the clean element weight to determine the total Dust Capacity.
The amount of dust retained by the filter is divided by the total amount of
dust fed during the test to determine the Cumulative Efficiency.
The K&N filter achieved the following results:
Dust Capacity: 305 grams
Cumulative Efficiency: 99.05 %
Holding the filter to the light is useless, pin holes are normal. That is
what makes a K&N filter. There are actually hundreds of microscopic fibers
that cross these holes and when treated with oil, capture and hold the very
fine particles. On the same hand, they allow the filter to flow more air
than paper or foam. The filter is 4 ply cotton gauze unlike some
competitors synthetic material filters. The synthetics do not have the very
small fibers that natural cotton does. Also, the oil can be pulled off of a
foam filter contaminating electronic sensors. It will absorb into cotton
and stay in the media. In fact, Honda and Toyota only recommend K&N filters
when using aftermarket high flow filters as K&N is the only brand of filter
the oil does NOT come off of. They will not cover a failed sensor if foam
filters were used.
We got started over 30 years ago making filters for motorcycles and off road
racers. The filters did so well that these guys wanted them for their cars
and trucks. We started making filters for these applications and here we
are today. If they did not work, we would not still be here and growing
We now make filters for Chrysler/Mopar, Ford Motorsports, Edelbrock, Rotax
Engines, and Harley Davidson. We come as original equipment on the 2000
Ford Mustang Cobra-R. We even made filters for the Apache helicopters used
in Desert Storm because of maintenance problems with the original paper
design. If they work in these conditions they will work for you. You may
post any or all of this if you like, in fact, it would be appreciated. I
would be interested in seeing the responses. Bottom line, don't believe all
you read or see on the Internet.
Thanks for writing, Rick
You can read it all right here:
And here's post using the same test but against oiled foam:
<A HREF="http://ceg.dyndns.org/archives/0103/msg00265.html" TARGET=_blank>[/URL]
And here's the same test but vs. foam:
1) I found this on the web. According to the author, this information is from Amsoil, so you have to take it with a grain of salt.
Here's the info I have on air filter performance. Tests were done using
SAE J726C Test Method 5-best --> 1-worst
Oiled foam Paper Oil Bath Oiled Gauze
(AMSOIL, UNI) (K&N)
Large particle efficiency 5 5 5 4
Small particle efficiency 5 4 1 2
Airflow capacity 5 2 3 5
Dust holding capacity 4 2 5 2
Load up characteristic 4 1 5 1
Backfire characteristic 3 2 5 3
Cleanability 4 1 4 3
As you can see, K&Ns are great for airflow, which is what they were
designed for. Their original application was on racing engines, where
airflow is important and ultimate engine life was of little consern. They
are not as good at filtering as paper or oiled foam types.
You can read this one here: [URL=http://brickboard.com/ARCHIVES/1997DEC/5909.shtml]</A>
With foam, there isnt a direct pinhole shot, it must travel through thousands of foam cells before reaching the engine. I wouldnt recommend using WD-40 oil though. Too light, not enough magnetic strength and dries up rather quick. Its good for one day running but I'd recommend cleaning it before another days worth. Use some thicker oil like castor oil made for fuel. Or alot of dirtbike shops carry this stuff.