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    Air filter choice.

    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?

    #2
    You can use the K&N without having to re-jet.

    1980 GS1000GT (Daily rider with a 1983 1100G engine)
    1998 Honda ST1100 (Daily long distance rider)
    1982 GS850GLZ (Daily rider when the weather is crap)

    Darn, with so many daily riders it's hard to decide which one to jump on next.

    JTGS850GL aka Julius

    GS Resource Greetings

    Comment


      #3
      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.
      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.

      .
      Last edited by Steve; 04-29-2017, 12:52 AM.
      sigpic
      mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
      hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
      #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
      #2 son: 1980 GS1000G
      Family Portrait
      Siblings and Spouses
      Mom's first ride
      Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
      (Click on my username in the upper-left corner for e-mail info.)

      Comment


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

        No re-jetting required.

        Comment


          #5
          K&N's flow more air because they are less restrictive and don't filter the air as well as other types of filters.
          Ed

          To measure is to know.

          Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

          Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

          Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

          KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

          Comment


            #6
            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.



            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.



            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.



            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.
            Last edited by KiwiAlfa156; 04-28-2017, 01:01 AM.
            sigpicDarryl from Kiwiland

            1982 GSX1100S Katana
            1982 GSX750S Katana
            1982 GS650G Katana

            Comment


              #7
              Go stock, as least save some money. You won't notice any difference on your 850.

              Comment


                #8
                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...

                Comment


                  #9
                  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?

                  Comment


                    #10
                    Originally posted by JJ View Post

                    Yes, Ed, I know their filtration is 3% less than the optimum filter, according to your source. Big fvcking deal...
                    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.
                    Ed

                    To measure is to know.

                    Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

                    Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

                    Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

                    KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

                    Comment


                      #11
                      Originally posted by Grog View Post
                      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?
                      Absolutely. The foam deteriorates and falls apart. With proper care it should last a couple of decades though.
                      Ed

                      To measure is to know.

                      Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

                      Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

                      Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

                      KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

                      Comment


                        #12
                        Originally posted by Grog View Post
                        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?
                        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:







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



                        The new filter looked a little bit better.



                        .
                        sigpic
                        mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
                        hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
                        #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
                        #2 son: 1980 GS1000G
                        Family Portrait
                        Siblings and Spouses
                        Mom's first ride
                        Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
                        (Click on my username in the upper-left corner for e-mail info.)

                        Comment


                          #13
                          Stock is the most reliable and durable. They make them that way for a reason. The GS850 is not a racebike.
                          NO PIC THANKS TO FOTO BUCKET FOR BEING RIDICULOUS

                          Current Rides: 1980 Suzuki GS1000ET, 2009 Yamaha FZ1, 1983 Honda CB1100F, 2006 H-D Fatboy
                          Previous Rides: 1972 Yamaha DS7, 1977 Yamaha RD400D, '79 RD400F Daytona Special, '82 RD350LC, 1980 Suzuki GS1000E (sold that one), 1982 Honda CB900F, 1984 Kawasaki GPZ900R

                          Comment


                            #14
                            Originally posted by Grog View Post
                            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?
                            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....
                            Last edited by KiwiAlfa156; 05-05-2017, 12:56 AM.
                            sigpicDarryl from Kiwiland

                            1982 GSX1100S Katana
                            1982 GSX750S Katana
                            1982 GS650G Katana

                            Comment


                              #15
                              i have a 79 GS850 can someone give me a part number for the stock air filter please and thank you.

                              Comment

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