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Air filter choice.

  • Thread starter Thread starter Grog
  • Start date Start date
G

Grog

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I have recently rescued a 79 gs850 from a friend's field of postponed projects. He tells me it was running when parked, but that was 7 years ago sitting in the Arizona sun. I intend to keep it as close to stock as I can. My first question has to do with the air filter. I am keeping the stock airbox, and I find both a sponge filter and a k&n filter available online. Can anybody tell me, if I use the k&n filter will I have to re jet my carbs or will everything still work like stock?
 
I have K&N inserts in my 850, my wife's 850 and my son's 1000. No re-jetting on any of them.

EDIT: Sorry, have to correct myself. :oops:
I have changed the main jets in my 850. Not because of the filter, but because of the header. The muffler is rather restrictive and very quiet. That header came with my son's 850 many years ago. The carbs also had larger jets in them. Before we sold his 850, we traded exhaust systems. My rusted-out and patched stock system went with his bike, I kept the header and the larger main jets. Embarassingly, I have never done proper plug chops to verify the jetting. At the last Ozark rally, I had a few comments that my exhaust was smelling rather rich, so I took out the 125s and dropped to just one size over stock, 117.5. Still haven't done plug chops, but the bike sure does run better.

Bottom line: stock mains for my 850 are 115, I am running 117.5. Stock pilot jets, needles are not shimmed, mixture screws are between 2 1/4 and 2 1/2 turns out.

.
 
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K&N factory replacement filters. I run them in my bikes and 4-wheeled vehicles.

No re-jetting required.
 
K&N's flow more air because they are less restrictive and don't filter the air as well as other types of filters.
 
Any replacement filter that doesn't require re-jetting flows no more air than the OEM filter. 'Performance'/washable filters that fit into the stock airbox don't require re-jetting for more fuel because its is the air box that is restricting airflow rather than the filter itself.

I was a true believer/user of K&N filters (mostly in modified intake systems) as they did require larger main jets and did offer measurable top end performance advantages until I realized that the airflow was increased because the filtration was significantly compromised.

image002.jpg


And regardless of the marketing spin, as the K&N got dirty air flow became really compromised, and it got dirty quickly. After washing and re-oiling the performance boost was like night and day. The problem with oiled cotton gauze is the big holes and small filtration area offered by of a couple of layers of cloth.

2012-05-20_13-12-59_222.jpg


If your seeing lots of daylight it because of big holes, these holes are bigger than the particles they are supposed to stop.
Here's the technical argument
And here's the independent test

So basically apart from being able to wash and reuse the filter, a drop-in oiled gauze filter offers you worse than OEM filtration with no performance advantage, and clog quickly due to their low dust holding capacity.

image012.jpg


My preference is for dual density oiled foam. They flow air, are wash and reuse, and offer performance gains as a pod. For a stock airbox your the best filtration is most likely to be OEM, if you want to wash and reuse in the stock airbox, then oiled-foam is a better bet.
 
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I don't use K&N stock-replacement filters for a performance increase. My GS's are stock. The Yamaha has a 4-1 pipe.

I use them because they last literally forever, with minimal maintenance.

Yes, Ed, I know their filtration is 3% less than the optimum filter, according to your source. Big fvcking deal...
 
Wow, that's a lot of information. Thanks everyone. The one knock I've heard on foam filters is the chance that as they age and deteriorate the can send foam particles into the intake. Is this an issue any one has seen in real life?
 
JJ said:
Yes, Ed, I know their filtration is 3% less than the optimum filter, according to your source. Big fvcking deal...
Click to expand...

Stay classy JJ. And BTW, it was not me that posted that link.

...however, speaking of the link, there are a lot of different tests and graphs in those links and there is a lot more to that testing than the simple statement that a K&N is 3% below optimal. A fair bit more dirt gets through to the engine using a K&N vs. a good paper filter. If you hang out on Bob Is The Oil Guy and read some oil analysis reports you will see some where the silica level is high in the oil, and the question posed back by the testing lab, Blackstone typically, is "do you have a K&N filter?" Read into that as you may but in my mind it's clear.
 
Grog said:
Wow, that's a lot of information. Thanks everyone. The one knock I've heard on foam filters is the chance that as they age and deteriorate the can send foam particles into the intake. Is this an issue any one has seen in real life?
Click to expand...

Absolutely. The foam deteriorates and falls apart. With proper care it should last a couple of decades though.
 
Grog said:
Wow, that's a lot of information. Thanks everyone. The one knock I've heard on foam filters is the chance that as they age and deteriorate the can send foam particles into the intake. Is this an issue any one has seen in real life?
Click to expand...
Well, I''m not sure how much was due to "age and deterioration" and how much was due to some "uninvited guests", but I worked on this bike recently:

IMG_2090_zps4a4o0atn.jpg


IMG_2092_zps8a7ykenx.jpg


IMG_2093_zpsylckk6g4.jpg


Good thing there is a screen behind the foam, or they might have gotten all the way into the carb.

IMG_2094_zpskluvccig.jpg


The new filter looked a little bit better. :encouragement:

IMG_2136_zpsxxzhqkkz.jpg


.
 
Stock is the most reliable and durable. They make them that way for a reason. The GS850 is not a racebike.
 
Grog said:
Wow, that's a lot of information. Thanks everyone. The one knock I've heard on foam filters is the chance that as they age and deteriorate the can send foam particles into the intake. Is this an issue any one has seen in real life?
Click to expand...

Oiled foam is stock on the GS650. Most off-road/moto-x bikes are oiled foam as stock. I can't think of any OEM bike filters that are oiled cotton. Yes, eventually they need to be replaced, but I don't think an oiled cotton gauze filter will survive the multiple washing it requires to maintain air flow, intact. If that were so your tee shirt would never wear out....
 
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i have a 79 GS850 can someone give me a part number for the stock air filter please and thank you.
 
srhbmx said:
i have a 79 GS850 can someone give me a part number for the stock air filter please and thank you.
Click to expand...

http://www.partsoutlaw.com/

This is the forum favorite parts source. I'm told if you use the discount code "BANG" you get cheap shipping.

I use Partzilla to order Kawasaki parts. They are also cheap for Suzuki parts but not quite as cheap as Parts Outlaw.
 
Little bit of necroposting here. Did the 82 GS850s use a foam element from the factory? There was a Uni filter in my Barnfind and some seams failed while cleaning it out. The foam seal on the metal frame was also deteriorated and fell apart. They don't seem to sell that part separately it seems. I figured something like some flatweather striping would do the same job in this case. Or do I need to just replace the whole filter frame? A replacement UNI element is less than 20 dollars and if the factory used Foam I see no need to drop x2-x3 the price for the factory element.
 
Downs said:
Little bit of necroposting here. Did the 82 GS850s use a foam element from the factory? There was a Uni filter in my Barnfind and some seams failed while cleaning it out. The foam seal on the metal frame was also deteriorated and fell apart. They don't seem to sell that part separately it seems. I figured something like some flatweather striping would do the same job in this case. Or do I need to just replace the whole filter frame? A replacement UNI element is less than 20 dollars and if the factory used Foam I see no need to drop x2-x3 the price for the factory element.
Click to expand...

Yes, stock is foam. And pretty sure the UNI doesn't include the frame.

Lots of guys using urethane whetherstripping foam to repair the airbox frame and airbox end caps. Basscliff may even have a tutorial.
 
I know it doesn't include the frame. My frame is serviceable other than the foam seal that was on it. Thanks for the info :)
 
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