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    Valve Lapping

    RE: lapping of the existing valves on the 81 GS850G, I'm told OK to lap the intake valves only but have also heard OK to also do the exhaust valves. Some thing about stellite material????? Valves & seats in pretty good state but wanted to get them seated perfectly as long as head is open.

    Thank you!

    DH

    #2
    Lapping is not to repair worn or damaged seats, it's only to clean them a little and check the seating pattern. Go easy and you will be fine.
    Ed

    To measure is to know.

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

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      #3
      You'll want to do both intake and exhaust.

      Comment


        #4
        Lapping both sets of valves should result in a line about 2 mm wide.

        Much wider than that and you're needing new seats cut


        You're replacing the valve stem seals while you're in there, right?
        1978 GS 1000 (since new)
        1979 GS 1000 (The Fridge, superbike replica project)
        1978 GS 1000 (parts)
        1981 GS 850 (anyone want a project?)
        1981 GPZ 550 (backroad screamer)
        1970 450 Mk IIID (THUMP!)
        2007 DRz 400S
        1999 ATK 490ES
        1994 DR 350SES

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          #5
          Valve lapping compound choices ??

          Comment


            #6
            Originally posted by Big T View Post
            Lapping both sets of valves should result in a line about 2 mm wide.

            Much wider than that and you're needing new seats cut


            You're replacing the valve stem seals while you're in there, right?
            I agree that 2mm is common for 8V engines (factory service limit is 1.4mm), yet most of these engines seem to seal up well anyway.
            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


              #7
              Originally posted by Russ' GS1000E View Post
              Valve lapping compound choices ??
              I like CLOVER brand in the green cans. It will come with 2 small cans, a can of coarse, & 1 of fine. Ray.

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                #8
                Forgot to say thanks. In the end my boss did them as I'm not smart enough (his view, fine by me) He had to cut all 4 ex seats in the end & lapped all 8 valves. Finished installing them last night & no leakage from any. I'm sure I would have messed up so glad for the help.

                Thanks again,
                DH

                Comment


                  #9
                  Originally posted by Nessism View Post
                  I agree that 2mm is common for 8V engines (factory service limit is 1.4mm), yet most of these engines seem to seal up well anyway.
                  I felt a slight rut around the valve when I lapped mine, and it was right at 2mm or a little more....

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                    #10
                    Originally posted by goggleboy View Post
                    I felt a slight rut around the valve when I lapped mine, and it was right at 2mm or a little more....
                    A rut like that is bad. You should get the valves faced.
                    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

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