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Air filter black with grime

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742 views 10 replies 6 participants last post by  Motorpsychology  
#1 ·
Hi Guys,
Any thoughts on why an air filter would look this way? (Blacked out with oil residue)
I’m used to seeing bugs, sand/dust and some pollen
Got this bike about 1,000 miles ago and decided on replacing the filter as it probably wasn’t done for 20K miles…
I was thinking oil overfill as the culprit
 

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#2 ·
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Are there wildfires close to where you live, or was the bike ridden in mostly in urban traffic? Lotta "heavy air" went through that filter. How does the underside of the filter look? Is there grime or a patina of oil in the intake or top cover? Airbox? Check the breather filter (#6) part # 13788-11J00 If it falls apart or is saturated with oily glop replace it and thoroughly clean the whole air box
That air filter might never have been changed, the way it looks.
 

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#4 ·
Check the breather filter (#6) part # 13788-11J00 If it falls apart or is saturated with oily glop replace it and thoroughly clean the whole air box
I was thinking the same thing. But in that case the underside of the air filter would become contaminated, not the top. Then again, it may have wicked into the air filter.

@PNW Vstrom 1000 do what @Motorpsychology said: check that this "breather filter" is in place and not disintegrating/missing. This "breather filter" is important: The crankcase vents to the airbox and that means that a fine oil mist will want to push up from the crank case via the breather hose into the air box. The "breather filter" (just a foam block) is a "coalescer": it traps the fine mist, turning it into larger droplets that will drip back into the crankcase by gravity. Without this filter the oil will be all over the inside of your air box, including the bottom of the air filter, and will burn in the engine - but not in enough quantity to notice any smoke.
 
#3 ·
Thanks
I just tossed it
I have a shop receipt saying they replaced it 35,000 km ago
The bike didn’t blow black smoke and I thought pulled well enough off the line…
After putting on a fresh filter I can defenitely feel the difference
What a fun improvement!
I’ll check back in a few thousand km and see if it blacked out again or not.
 
#6 ·
Found it (apparently I kept it for future reference)
Checked again the service record from the previous owner and it was supposed to have been replaced at 67,800km…
I just replaced it at 86,600 and I just don’t understand how it would get so black on top and yet looks almost pristine underneath.
In my 35 years of riding and changing air filters for myself and others, never seen anything this weird.
Bike was running clean but is noticeably more torquey with the new filter in place.
 

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#7 ·
Looking at the two photos, the filter was doing an excellent job of protecting the engine.
 
#9 ·
Very common look of a filter with some miles on it. Yes, the emissions systems on bikes have crankcase gasses emitted to an outlet in the air box. Mixes with atmosphere and ( in theory) some of the compounds will get burned up when cycled back through the combustion chambers. That fine mist, which is going to have engine oil as well as some gasoline compounds, is going to settle on the air filter. That will cause dirt/dust to adhere to it. Which is the black you see. The filter is doing its job. In older engines with a lot of "blowby" it can get so bad that the air filter can get saturated!