Replacing valve seals, which one?

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  • overboostin
    • Feb 2026

    #1

    Replacing valve seals, which one?

    I've had some smoke out of my left hand pipe which I've figured is most likely a valve seal. Is there an easy way to tell which specific seal it is or should I just go through and replace all 8?
  • Agemax
    Forum Guru
    • Apr 2008
    • 8371
    • plymouth uk

    #2
    if 1 needs replacing then you can bet they all do.
    replace the lot and be done with it. a good head and valve overhaul will be a good idea while you are at it
    1978 GS1085.

    Just remember, an opinion without 3.14 is just an onion!

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    • hampshirehog
      Forum LongTimer
      Past Site Supporter
      • Oct 2007
      • 12675
      • Hampshire. UK

      #3
      If you are sure it's a valve seal then the usual thing is to replace all of them on the basis that if one has hardened then the others aren't far behind.
      79 GS1000S
      79 GS1000S (another one)
      80 GSX750
      80 GS550
      80 CB650 cafe racer
      75 PC50 - the one with OHV and pedals...
      75 TS100 - being ridden (suicidally) by my father

      Comment

      • Steve
        GS Whisperer
        • Jun 2005
        • 35925
        • southwest oHIo

        #4
        Look at it this way: each seal is only a couple of bucks.

        The gaskets to take the engine apart and put it back together to change the seals are over $100.

        How many times do you want to do the job?

        .
        sigpic
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        #2 son: 1980 GS1000G
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        • overboostin

          #5
          Yeah that's what I figured would be best. It's a shame because the engine only has 14k on it. I think it was just sitting for awhile.

          Comment

          • hampshirehog
            Forum LongTimer
            Past Site Supporter
            • Oct 2007
            • 12675
            • Hampshire. UK

            #6
            If it's just valve seals you can ride it anyway if it isn't belching smoke out or drinking too much oil.
            79 GS1000S
            79 GS1000S (another one)
            80 GSX750
            80 GS550
            80 CB650 cafe racer
            75 PC50 - the one with OHV and pedals...
            75 TS100 - being ridden (suicidally) by my father

            Comment

            • overboostin

              #7
              Apparently it smokes quite a bit from the left pipe when I'm on it. Not much at idle but my buddy said when I was riding it was pretty smokey.

              Comment

              • overboostin

                #8
                I didn't put many miles on it at all last season and it had been sitting before that. Do you think I should just ride it and see if it works itself out first? Maybe a seal needs to loosen up?

                Comment

                • koolaid_kid

                  #9
                  I strongly suggest you do a compression test.

                  Comment

                  • Guest

                    #10
                    Valve seals will smoke at startup and when you close the throttle when riding.
                    If it smokes on accel most likely it's rings.

                    Comment

                    • koolaid_kid

                      #11
                      Originally posted by chef1366
                      Valve seals will smoke at startup and when you close the throttle when riding.
                      If it smokes on accel most likely it's rings.
                      That was my thought as well, hence the suggestion for a compression check. Although, if just the oil ring is stuck, it may still have good compression.

                      Comment

                      • overboostin

                        #12
                        I know it would be hard to determine from this but do you think it's likely that they just need to be broken free with riding or they need to be replaced?

                        Comment

                        • koolaid_kid

                          #13
                          The answer to that question is a resounding "Yes".

                          IOW, it is impossible to tell. Some have squirted Marvel Mystery Oil down there to try to loosen them.

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                          • Nessism
                            Forum LongTimer
                            GSResource Superstar
                            Past Site Supporter
                            Super Site Supporter
                            • Mar 2006
                            • 35790
                            • Torrance, CA

                            #14
                            Make sure the smoke is oil too before pulling down the engine. Black smoke is due to the carbs, it's white-bluish smoke that's from oil.
                            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

                            • gs850cafe

                              #15
                              Originally posted by chef1366
                              Valve seals will smoke at startup and when you close the throttle when riding.
                              If it smokes on accel most likely it's rings.
                              so thats y i smoke everyone out behind me when were playing

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