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new head gasket on GS550 results in oil dripping from front 10mm screw

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    #16
    So what do folks think of this type of head gasket:



    I had this left over from a gasket kit. It looks like two pieces of steel with a black composite material in between. It measures 1mm thick. The OEM measured 1.25mm.

    That extra .25mm may be why it's leaking even though I used the o-ring.
    Last edited by DimitriT; 04-18-2021, 12:21 PM.

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      #17
      That's a MLS gasket.
      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

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        #18
        Originally posted by Nessism View Post
        That's a MLS gasket.
        ok so the OEM gaskets don't have that composite core and they are stamped with "TOP"?

        For MLS gaskets, which side goes up?

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          #19
          So I tore into it today and here's what I found:

          1. the surfaces are clean, flat and smooth. I mean you cannot tell there's new sleeves in there.

          2. since I was using a NOS OEM gasket (I measured it at 1.25mm thick, BTW) I added the four o-rings in the corners, plus the middle o-ring.

          3. somehow I ended up with two sizes of corner o-rings: 1.15mm thick and 1.45mm thick.

          4. one of the corners (cylinder #1, front) had a thinner o-ring - aha, there's your problem.

          Now the MLS gasket I have is 1mm thick and maybe those thinner o-rings were meant for that type of gasket, I don't know. But using the OEM gasket with the thin o-rings is never going to seal.
          Last edited by DimitriT; 04-18-2021, 03:31 PM.

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            #20
            Am I understand correctly that you reused the original OEM gasket that came on your bike 40 years ago?
            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

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              #21
              Originally posted by Nessism View Post
              Am I understand correctly that you reused the original OEM gasket that came on your bike 40 years ago?
              No, I found a new old stock OEM on ebay.

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                #22
                So I reassembled it with the OEM head gasket and the thicker o-rings. I also applied a bit more sealer around the rectangular o-ring and a light coating of sealer on the outer edges of the mating surfaces of the head gasket. Since I didn't remove the block, I didn't disturb the base gasket so I hope that doesn't give me trouble.

                Compression checks out: (130, 120, 120, 125, dry and cold) it used to be (80, 60, 85, 85) before the new sleeves

                I prepped the base gasket by applying a light coat of general purpose grease on both sides everywhere, and some sealer on both sides of the corner portions which contain the oil galleys - I've never had a leak with this prep and the old gasket comes off without the usual ball-busting).

                So I still went ahead and ordered a NOS OEM head/base gasket in case the reuse attempt fails. I ran the bike briefly and no leaks yet. Next I'll sync the carbs again and do some road testing.

                My plans for this bike are to transport it to Florida and keep it at my parents house for use when I am down there. I've had this bike for 16 years and put over 50k miles on it. Most likely it will go into the estate sale.
                Last edited by DimitriT; 04-19-2021, 09:18 AM.

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                  #23
                  So far so good as far as leaks go. It's not insured/registered yet so I can't really go for a long ride but a few launches up and down a country road feel really strong. Much stronger than with the old sleeves.

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