Air filters – all that glitters is not gold

Air filters do a very crucial job, that’s a no-brainer. You don’t need deep insight to realize the air filtration system also require frequent attention.

The norm is to change air filter at service intervals for your motorcycle. But if you ride offroad, on gravel or dirt, it might be sensible to inspect more frequently. In fact, VERY sensible. Change air filter more often. A dirty air filter affects breathing of your engine, causes harmful emissions, damaged spark plugs. Just to mention a few things.

Air filters: BMW R1200GSA Air filter, 7600km.

BMW R1200GSA Air filter, after 7600km. Yes I ride offroad

Air filters, what to choose

Some would say, stick to stock. As I now know, with good reason. Allegedly there are better solutions out there. Or are they really better? if you search online, you find lots of options. Of all these options K&N is one brand that ranks high on various types of searches. So that name and brand got my attention.

At first web-glance, one could easily be led to believe their filters are almost perfect solutions. Whether for cars, trucks, or motorcycles.

K&N air filters are coated with oil. The claim is that this, combined with the design of the filter itself, helps on engine breathing while trapping harmful particles.  Thus it improves performance without at the expense of air filtration, or filtration quality.

You can re-use the filter, by washing and re-apply an oil coating.  This done with a branded re-charger kit.

First I saw just positive remarks. And videos. Many sang the praise of these washable, reusable oil based filters. It almost had me wonder why these type of filters weren’t standard on all vehicles.

One such positive impression you can watch below. I also read comments, without claiming that necessarily helps. Here is an article  also very favorable of the K&N products.

The praise won me over. Too soon. Sometimes I am too hasty for my own good. Too impulsive, the sort that acts first, and then goes into nagging doubts mode. 

Ordered, with doubts

I continued doing research. Digging deeper I found far less favorable articles, content, or comments. Should I have done more thorough research  before purchase? Yes absolutely.

The internet is, as we all know,  full of “apples and oranges” comparisons.  It is not always easy to tell the guiding and the misleading apart. Sometimes the misleading is aided by well constructed web documents that ranks well. Written or authored by professionals.

Lies sometimes trumps or defeats truth. But truths are, or can be, like lies, subjective.

You’d think, if a formula was not good, that  a manufacturer would change specs over the years. Improve their products. Disclaimers weavers the manufacturers right to do so without explicitly stating what has been changed.

Surely, was there something fishy about the filters, then they would have changed or improved them? Maybe even several times?  Well to tell you the truth, my uncertainty didn’t fade or wane.

K&N BM-113 Air filter for BMW R1200GS Adventure

K&N BM-113 Air filter for BMW R1200GS Adventure

K&N air filter installed

Mid-May the filter arrived in the mail. A few days later I put it in. The old filter (above) looked done for. At first I thought I could notice, ever so slightly,  a difference in engine response. Wondered if It sounded differently too, but that might have been my imagination.

During the “post-purchase” research I kept on finding unfavorable documentation. Some directly warning people not too buy K&N or any oil based air filter. Some of the stuff I found was downright scary. Well you know the drill I suppose. When in doubt, play safe.

As a result I made the decision not to ride offroad till after the bike had been on service. This way reduce any risk of contamination or damage caused by poor filtering. The motorcycle was up for its 40.000 kilometer service in June. Since going south on another adventure  I had booked service in England.

Mid June I left Norway and started the journey south. A few days later the bike had its big service at Allan Jeffries in South Yorkshire, England. I had a talk with a service engineer prior to service and asked them to inspect air filter box, intake and filter. At the time the bike had done around 2.250 kilometers with the K&N air filter.

Luckily they found no debris, and no oil residue in the air filter box.  So no harm done.

Air filters: my 180 degrees turn

I had decided before leaving home to change back to paper air filter. The service engineer supported the decision.  The bike was fitted with a stock air filter. This has since done 10.000 kilometers, on and offroad.

Why the turnaround? Well many reasons, some of these reasons are eloquently summed up in the video below.

This is a professional mechanic who should know his business. See also his other videos:

Now imagine what could happen if you put such a filter in a bike that is used a lot offroad, possibly in very dry, dusty conditions.  I ride quite a lot on gravel and dirt. Norway & Sweden combined is gravel territory.  And I am definitely an adventure motorcycle type of guy.

Because of this I need a air filter solution I can fully trust. So apart from the stock filter, are there any sensible options? Well yes maybe.

Fast forward to December 2019. My motorcycle is now in winter storage. I turned it in late October. The season was over, at least for me. And the bike needed its 50.000 kilometer service. Perfect timing really. Stock air filter will be replaced with stock air filter.

Come spring, I might try one new filter that supposedly beats the stock. A paper filter, composed of the same materials as the OEM. But with better seal. Well, we shall see.

HiFloFiltro HF7915 for BMW R1200GS/GS Adventure

HiFloFiltro HF7915 for BMW R1200GS/GS Adventure

This time I intend to all my research before making a decision. The winter is (unfortunately) quite long up here in the north.

Additional comments

I thought about including the below when writing the post but left it out. Then changed my mind.

Based on the below video, showing oil and debris in the filter box, it seems highly likely that the filter had been over-saturated with oil after cleaning. My filter had not spilled any oil into the air filter box. But it was almost brand new and had only been in for a month.

Yet the mechanic claims that ugliness is something he sees “every time” he inspects a bike with a similar air filter.  If true then the biggest unknown in the equation must the person cleaning or servicing the filter.

The filter surface, the mesh, the composition characteristics, probably also change over the course of the life cycle.  And the oil absorption coefficient change. Which again can cause deterioration and further contamination.

Herein lies some unknowns. What if the cleaning is done poorly? What if too much oil is added, like the videos show? How long does it take before significant damage is done to the engine? What if oil + particles is sucked into the engine? The answer to that question is, potentially, in the video above.

Conclusion? if buying  a second hand motorcycle, ask about the air filter. What has been used. if paper/cotton, stock or similar, less reason for concerns.

I think it is safe to say, regardless, better to stay in the dry.

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