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    Timing Chain Jump at Crankshaft

    This is a continuation of my thread at http://www.thegsresources.com/_forum...ve-not-seating about the loss of compression in the #3 cylinder and sudden poor running of the engine. I took a look at the timing tonight, not good. The timing jumped and most likely bent at least this one valve enough to prevent it from closing.

    The two cams are still aligned and the correct number of chain pins between the timing marks, but the crankshaft is not at TDC any more... the cams are ahead of the crankshaft.

    Scenario on the road when this problem occurred: back road, traveling about 35 mph around a somewhat blind curve and a car pulled out in front of me. Not quite an emergency stop, because I was able to hit the horn while rapidly slowing down behind this car, but that was the end of the good running engine. I was downshifting quickly, and braking hard, but would that have caused the chain to jump on the crankshaft?

    Pictures will be added in following posts since I can't add more than one at a time.

    Dave
    Attached Files
    Blog of my motorcycle projects - http://twowheeljunkie.wordpress.com/
    1981 Suzuki GS650L - Project Bike - Sold
    2013 Suzuki SFV650 - Sold
    2016 Ducati Multistrada 1200 Touring

    #2
    Exhaust cam mark 1 aligned with head gasket.

    IMG_5018.JPG
    Blog of my motorcycle projects - http://twowheeljunkie.wordpress.com/
    1981 Suzuki GS650L - Project Bike - Sold
    2013 Suzuki SFV650 - Sold
    2016 Ducati Multistrada 1200 Touring

    Comment


      #3
      Marks 2 and 3, 20 pins apart.

      IMG_5019.JPG
      Blog of my motorcycle projects - http://twowheeljunkie.wordpress.com/
      1981 Suzuki GS650L - Project Bike - Sold
      2013 Suzuki SFV650 - Sold
      2016 Ducati Multistrada 1200 Touring

      Comment


        #4
        Crankshaft not at TDC.

        IMG_5025.JPG
        Blog of my motorcycle projects - http://twowheeljunkie.wordpress.com/
        1981 Suzuki GS650L - Project Bike - Sold
        2013 Suzuki SFV650 - Sold
        2016 Ducati Multistrada 1200 Touring

        Comment


          #5
          Rotate crankshaft to TDC, Marks 2 and 3 rotated ahead.

          IMG_5028.JPG
          Blog of my motorcycle projects - http://twowheeljunkie.wordpress.com/
          1981 Suzuki GS650L - Project Bike - Sold
          2013 Suzuki SFV650 - Sold
          2016 Ducati Multistrada 1200 Touring

          Comment


            #6
            Crankshaft now at TDC.

            IMG_5029.JPG
            Blog of my motorcycle projects - http://twowheeljunkie.wordpress.com/
            1981 Suzuki GS650L - Project Bike - Sold
            2013 Suzuki SFV650 - Sold
            2016 Ducati Multistrada 1200 Touring

            Comment


              #7
              Seems the problem was the tentioner stuck or has broke. And yes the chain could jump at the crank as slack.... or whip if you will..happened. Time to yank the head and get it right again would be my approach.
              Last edited by chuck hahn; 02-28-2017, 11:31 PM.
              MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
              1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

              NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


              I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

              Comment


                #8
                Looks like I have plenty of work to do now!
                Blog of my motorcycle projects - http://twowheeljunkie.wordpress.com/
                1981 Suzuki GS650L - Project Bike - Sold
                2013 Suzuki SFV650 - Sold
                2016 Ducati Multistrada 1200 Touring

                Comment


                  #9
                  On at least half the cam chain tensioners I've encountered, someone has tightened the locking screw against the pushrod, therefore ensuring that the tensioner can't work.



                  No idea whether this is a partial explanation for what happened to your bike, but definitely pay attention to the state of the tensioner when you remove it.
                  1983 GS850G, Cosmos Blue.
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                  Comment


                    #10
                    The previous owner had the bike for 30 years. I don't think he did anything except for oil changes and tires, so everything else is just age and neglect.

                    Thanks for the link on the tensioner re-build. Your site is invaluable.

                    Dave
                    Blog of my motorcycle projects - http://twowheeljunkie.wordpress.com/
                    1981 Suzuki GS650L - Project Bike - Sold
                    2013 Suzuki SFV650 - Sold
                    2016 Ducati Multistrada 1200 Touring

                    Comment


                      #11
                      If it skipped at the crank, shouldn't the crank be ahead of the cams??
                      Jordan

                      1977 Suzuki GS750 (My first bike)
                      2000 Kawasaki ZRX1100
                      1973 BMW R75/5

                      Comment


                        #12
                        Originally posted by hannibal View Post
                        If it skipped at the crank, shouldn't the crank be ahead of the cams??
                        Hard braking ,sudden engine speed decrease,any chain slop could go either way on crank.
                        1981 gs650L

                        "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

                        Comment


                          #13
                          Pulled off the head today. The chain guide for the cam tensioner is snapped in half right where the tensioner would press against it.

                          IMG_5042.jpg

                          Does not look like much availability for this part...
                          Blog of my motorcycle projects - http://twowheeljunkie.wordpress.com/
                          1981 Suzuki GS650L - Project Bike - Sold
                          2013 Suzuki SFV650 - Sold
                          2016 Ducati Multistrada 1200 Touring

                          Comment


                            #14
                            Bunch of used ones on Ebay..



                            Bikes that used that same PN...


                            Last edited by chuck hahn; 03-05-2017, 05:04 PM.
                            MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
                            1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

                            NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


                            I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

                            Comment


                              #15
                              I have ordered one. Hope it is in good shape.
                              Blog of my motorcycle projects - http://twowheeljunkie.wordpress.com/
                              1981 Suzuki GS650L - Project Bike - Sold
                              2013 Suzuki SFV650 - Sold
                              2016 Ducati Multistrada 1200 Touring

                              Comment

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