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    GS 750 to 850 Conversion Issue

    Hi,

    I just did a 850 conversion on my 77' 750 with no real issues other than when it hits about 3,000 rpms it starts kicking oil out through the breather cap. Does anyone have any suggestions on how to solve this? Since i'm going to be running K&N pods that breather line is going to be just dangling, so I figure I can create a makeshift dry sump system by mounting an oil overflow tank below the breather cap / above the oil filler cap and tap and run the appropriate lines.

    Thoughts?
    Last edited by Guest; 05-09-2018, 03:40 PM.

    #2
    How much oil? A bit of oil mist is not uncommon, but actual liquid oil could indicate a problem.
    I think there should be some type of filter type material under the cover where the hose connects. Perhaps its missing?

    Edit / add - parts fische for an 850 show four oil separators under the cover.
    Last edited by dorkburger; 05-09-2018, 04:21 PM.
    sigpic
    When consulting the magic 8 ball for advice, one must first ask it "will your answers be accurate?"

    Glen
    -85 1150 es - Plus size supermodel.
    -Rusty old scooter.
    Other things I like to photograph.....instagram.com/gs_junkie
    https://www.instagram.com/glen_brenner/
    https://www.flickr.com/photos/152267...7713345317771/

    Comment


      #3
      it's actual oil not a mist. I have the mesh screens and the gasket under the breather..

      Comment


        #4
        How much oil did you put in the sump?

        There shouldn't be any real pressure in the crankcase, so if you DO have pressure, the only source is blow-by coming past the rings.

        .
        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.)

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          #5
          3.5 liters as per the manual with a filter change. I'm planning on doing a compression test. I should be hoping for 130 PSI warmed up, right?

          Comment


            #6
            Not sure if the numbers, but the test should be done with the throttle wide open to get proper numbers.
            sigpic
            When consulting the magic 8 ball for advice, one must first ask it "will your answers be accurate?"

            Glen
            -85 1150 es - Plus size supermodel.
            -Rusty old scooter.
            Other things I like to photograph.....instagram.com/gs_junkie
            https://www.instagram.com/glen_brenner/
            https://www.flickr.com/photos/152267...7713345317771/

            Comment


              #7
              Originally posted by KornGirl666 View Post
              3.5 liters as per the manual with a filter change. I'm planning on doing a compression test. I should be hoping for 130 PSI warmed up, right?
              That's about right. The main thing is even numbers between the cylinders, with about 10-15% difference allowed. Like Glen said make sure you open the throttle all the way and a fully charged battery.
              GSRick
              No God, no peace. Know God, know peace.

              Eric Bang RIP 9/5/2018
              Have some bikes ready for us when we meet up.

              Comment


                #8
                Got a chance to do a compression test over the weekend.

                Here are the "dry" readings.

                Cyl 1: 100
                Cyl 2: 105
                Cyl 3: 108
                Cyl 4: 120

                "Wet" readings with 1 ounce of oil in each.

                Cyl 1: 130
                Cyl 2: 125
                Cyl 3: 135
                Cyl 4: 137

                So i'm obviously loosing compression through the bottom end. My question now is: How can I tell if it's the jugs or the rings? The rings are brand new and I did a hone on the cylinders before assembling. Any suggestions for tests / what to look for?

                Comment


                  #9
                  If you have new rings and a fresh hone job, how many miles on the engine since that work was done?

                  Unless you have several hundred miles on it, breaking it in PROPERLY, and those are cold numbers, they look pretty decent.

                  .
                  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


                    #10
                    Yeah, it may take care of itself once the rings and cylinders get reacquainted with each other.
                    GSRick
                    No God, no peace. Know God, know peace.

                    Eric Bang RIP 9/5/2018
                    Have some bikes ready for us when we meet up.

                    Comment


                      #11
                      15 minutes of idle runtime on it only. I guess i'll have to create a temporary wet sump system to break it in.

                      Comment


                        #12
                        Originally posted by KornGirl666 View Post
                        15 minutes of idle runtime on it only. I guess i'll have to create a temporary wet sump system to break it in.
                        There is a break in technique that needs to be followed. Some say take it easy and alternate speeds while never staying at one rpm for any length of time for multiple 15 minute intervals with a cool down time in between and others will say run it like you stole it. I've also hear people say to use oil with a high zinc content and to never use full synthetic. It's too slick to let the rings get the friction needed to form to the cylinder walls.
                        GSRick
                        No God, no peace. Know God, know peace.

                        Eric Bang RIP 9/5/2018
                        Have some bikes ready for us when we meet up.

                        Comment


                          #13
                          Correct on the synthetic.
                          Current Rides: 82 GS1100E, 00 Triumph 955 Speed Triple, 03 Kawasaki ZRX1200, 01 Honda GL1800, '15 Kawasaki 1000 Versys
                          Past Rides: 72 Honda SL-125, Kawasaki KE-175, 77 GS750 with total yosh stage 1 kit, 79 GS1000s, 80 GS1000S, 82 GS750e,82 GS1000S, 84 VF500f, 86 FZR600, 95 Triumph Sprint 900,96 Triumph Sprint, 97 Triumph Sprint, 01 Kawasaki ZRX1200, 07 Triumph Tiger 1050, 01 Yam YFZ250F
                          Work in progress: 78 GS1000, unknown year GS1100ES

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                            #14
                            Finally got a chance to ride the bike around the block for a few hours and oil is still spewing out of the breather box hose on top of the valve cover. Any information on what is happening, and how to solve this would be great. As mentioned above the compression numbers seem decent.

                            Comment


                              #15
                              That is about normal and from what I have read, most people with pods (I don't have them) will attach a separate filter to the breather hose
                              sigpic
                              Cowboy Up or Quit. - Run Free Lou and Rest in Peace

                              1981 GS550T - My First
                              1981 GS550L - My Eldest Daughter's
                              2007 GSF1250SA Bandit - My touring bike

                              Sit tall in the saddle Hold your head up high
                              Keep your eyes fixed where the trail meets the sky and live like you ain't afraid to die
                              and don't be scared, just enjoy your ride - Chris Ledoux, "The Ride"

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