Flat to round air filter conversion

[Mal S7]

Don't fret jeff. Bit o' dust n insects in there is good, keeps them moving parts nicely bedded for more performance. Don't let 'em tell you otherwise.

[SteveD]

SteveD, that page is great. It certainly makes it clear why K&N's are popular: they flow more air. Thus, K&N's are the most likely filter to require jetting changes. It also makes it very clear HOW the K&N flows more air: by letting in a lot more dirt.

And despite that, I use one.

I've had it for years, and periodically I remove it for a pleated paper filter, but it went back in when I fitted the less restrictive Jim Cray mufflers. It rarely gets washed, but is regularly inspected to have anything solid removed, eg insects, and it'll then get a spray of the prescribed filter oil. In all that time the inside of the airbox has remained remarkedly clean. A finger swipe over the surface only ever reveals a very slight film of oil from the breather. It's also had the modification at the front so that it seats and seals correctly.

[Major Softie]

And despite that, I use one.

I've had it for years, and periodically I remove it for a pleated paper filter, but it went back in when I fitted the less restrictive Jim Cray mufflers. It rarely gets washed, but is regularly inspected to have anything solid removed, eg insects, and it'll then get a spray of the prescribed filter oil. In all that time the inside of the airbox has remained remarkedly clean. A finger swipe over the surface only ever reveals a very slight film of oil from the breather. It's also had the modification at the front so that it seats and seals correctly.

We've speculated here in past discussions that the K&N may well do a decent job of filtering after it has gotten dirty. The tests prove the complete opposite. That was the most surprising part to me.

[SteveD]

And despite that, I use one.

I've had it for years, and periodically I remove it for a pleated paper filter, but it went back in when I fitted the less restrictive Jim Cray mufflers. It rarely gets washed, but is regularly inspected to have anything solid removed, eg insects, and it'll then get a spray of the prescribed filter oil. In all that time the inside of the airbox has remained remarkedly clean. A finger swipe over the surface only ever reveals a very slight film of oil from the breather. It's also had the modification at the front so that it seats and seals correctly.

We've speculated here in past discussions that the K&N may well do a decent job of filtering after it has gotten dirty. The tests prove the complete opposite. That was the most surprising part to me.

The tests certainly show increased flow of dirt. Many have therefore suggested engine longevity would be shortened. As a piece of research it seems ok, (the purolator wasn't sealed correctly though) but there are limitations to the conclusions that may be drawn.

The study doesn't test engine longevity under those test conditions. That'd be the ideal, but unlikely study as that would mean high cost and multiple engines with different filters under different conditions. Has anyone ever paid for that study?

It seems obvious that more dirt would increase engine wear, but under the study circumstances how is this proven? Is it not a leap from one conclusion to another? How much dirt, and of what particulate size and characteristics, is needed to decrease engine life? At what rate does it decrease engine life? I'm guessing someone out there has that info. How might it correlate to the air & dirt flow thru a K&N? What happens in the combustion chamber to the fine particulate that gets thru? The study shows that they all pass the dirt.

Variables like how the bike is used, environment it's used in, quality of oil used, frequency of oil changes, type of oil filters also have influence on engine wear.

My thought is that it comes down to an individuals own risk analysis re: their usual use and care of their bike. For me it means modifying the filter to ensure it seals, increasing frequency of oil and filter changes and regular oiling of the filter to keep it at it's best performance. It seems it shouldn't be allowed to diminish that in any way.

After last years Boxerworks Talbingo ride, where I followed Hans (Ontic) down 50-60ks of very dusty roads, I did inspect the filter when I got home. The inner casing was clean, so I just tapped the country bugs out of the filter, gave it a little more oil and put it back in. Of course, that's an unscientific test, but it's what I do. If I was headed outback or down multiple dirt roads, then I'd probably put a paper filter in despite the clean air box.

[KenHawk]

I had a K+N round filter in my R90 but when I rebuilt the bike I gave it away.

Theres simply no way I'm going to invest big $$$$ into my engine and then install a K+N foam non-filter. I might be crazy but...

[SteveD]

Those foam ones are no good. Everyone knows that!

[DanielMc]

I stripped down a Guzzi Le Mans that had run with totally unfiltered Dell'Ortos for nearly 70k miles and there were no unpleasant surprised with the heads or valves and no scoring or excessive wear on the (cast iron) bores. Things would probably have been different if the bike had been running around sand or grit, but on the damp clean roads of the UK it seemed to have come to no harm.

[Major Softie]

Theres simply no way I'm going to invest big $$$$ into my engine and then install a K+N foam non-filter. I might be crazy but...

K&N are oiled cloth, not foam. The Uni-filters we were also talking about are foam.

[chasbmw]

If you are riding on country roads in OZ it is very obvious if your filter is not filtering as the dust gets everywhere. I used oiled foam filter when I went round OZ and it seemed to work pretty well.

I use a K&N on my 1070 bike and a standard BMW paper on the 900.

If you want to increase airflow through a flat BMW filter housing, drill 4x1" holes in the top and cut the intake snow kneels down to half the standard length. You will need to fit a K&N filter as they will be better at dealing with rain etc etc.

[Unclviny]

I would NEVER run a K&N filter on ANYTHING or buy a vehicle that used one, there is a reason that they flow-good, because they do not filter anything other than Children, Dogs and small-rocks.

Vince