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  • Crankshaft question

    Hey guys, I listed earlier about problems with my 93 GTX. I have a problem with compression leaking back through the back cylinder intake and through the carb barrel. After removeing the rotery valve case I noticed that the forward cylinder(which seams to run good)valve timing is right but the back cylinder is wrong.How is that possible. Are the crankshaft lobes exactly 180 degrees apart. I can put a screwdriver in the forward cylinder and when it is at TDC the back cylinder is not at BDC. It is about 25 degrees off. Is it possible for the crankshaft main journals to move. Thanks for your help.
    93 SEADOO GTX
    OIL BLOCKOFF KIT
    DG EXTREEME PERFORMANCE PIPE &WATERBOX
    DG REV LIMITER SET AT 7,000RPM

    95 SEADOO XP
    NEED MOTOR.....
    EMAIL IF U HAVE A BLOWN ONE FOR SALE
    OR REBUILT ONE

  • #2
    Re: Crankshaft question

    Yes! As i understand, cranks are pressed together under tonnes of pressure during construction. As they are made of individual parts, it is possible for the crankshaft to become out of phase. You need to get yourself a new/rebuilt crank that has exactly 180 degress phase difference, otherwise you will have engine problems/damage.

    Comment


    • #3
      Re: Crankshaft question

      Yep, you have the old 1993 657 twisted crank syndrome. 1993 was the only year SD used that pos crank, the one with the big holes in the counterbalancer wheels.
      Find a 657X crank and it will never twist.
      Bill O'Neal <br>
      WCM
      <a href="http://www.watercraftmagic.com"

      Comment


      • #4
        Re: Crankshaft question

        Hey Bill, It is acually the 587 engine. Does that have the same problem with the crankshaft? Thanks.
        93 SEADOO GTX
        OIL BLOCKOFF KIT
        DG EXTREEME PERFORMANCE PIPE &WATERBOX
        DG REV LIMITER SET AT 7,000RPM

        95 SEADOO XP
        NEED MOTOR.....
        EMAIL IF U HAVE A BLOWN ONE FOR SALE
        OR REBUILT ONE

        Comment


        • #5
          Re: Crankshaft question

          1993 GXT's have 657 engines in them.
          Any crankshaft can get twisted though. Some are more prone to twisting than others.
          Bill O'Neal <br>
          WCM
          <a href="http://www.watercraftmagic.com"

          Comment


          • #6
            Re: Crankshaft question

            Bill,

            Just out of interest, is a 720 crank prone to twisting? My ski is a 95XP. I kept the original crank for the rebuild and had the PTO and mag flywheel bearings replaced only as it met all tests for out run (tru test), conrod straightness, phase, etc.

            Comment


            • #7
              Re: Crankshaft question

              Thanks for all your help guys. I am going to take the engine apart this week. Do you think I can have the crankshaft repaired or should I just buy an overhauled one. Also, we connected a aftermarket rev limiter on this ski and the first time we connected it wrong. We connected the red/black wire to the CDI rather than the coil. Could this cause preignition which could of been the cause of the crank damage. Is there anything that controls fireing order. For example, I connected the aft cylinder spark plug lead to the forward cylinder and it ran fine on that one cylinder. (the back cylinder was not connected). Are they constantly fireing. Thanks.
              93 SEADOO GTX
              OIL BLOCKOFF KIT
              DG EXTREEME PERFORMANCE PIPE &WATERBOX
              DG REV LIMITER SET AT 7,000RPM

              95 SEADOO XP
              NEED MOTOR.....
              EMAIL IF U HAVE A BLOWN ONE FOR SALE
              OR REBUILT ONE

              Comment


              • #8
                Re: Crankshaft question

                Buy a rebuilt crankshaft.
                No the wrong wiring did not hurt the CDI and it could not change the firing order. The coil fires both sparkplugs at exactly the same time. It matters not which clyinder you run the sparkplug wire to.
                Last edited by Bill O'Neal2; 01-25-2006, 01:44 PM.
                Bill O'Neal <br>
                WCM
                <a href="http://www.watercraftmagic.com"

                Comment


                • #9
                  Re: Crankshaft question

                  I was wondering should i just get my crankshafted twisted back and tig welded. i have a local shop that will do it for $70 bucks. Or do u recommend someting else bill? is so please give me some places to look thanks Adam
                  93 SEADOO GTX
                  OIL BLOCKOFF KIT
                  DG EXTREEME PERFORMANCE PIPE &WATERBOX
                  DG REV LIMITER SET AT 7,000RPM

                  95 SEADOO XP
                  NEED MOTOR.....
                  EMAIL IF U HAVE A BLOWN ONE FOR SALE
                  OR REBUILT ONE

                  Comment


                  • #10
                    Re: Crankshaft question

                    Swap your damaged crank with an SBT remanufactured crank....it is very possible that there are more damaged parts to the crank (conrods, bearings, etc) so therefore i don't recommend that you do a quick fix. Get yourself a new crank that is up to spec.

                    Comment


                    • #11
                      Re: Crankshaft question

                      Without personally seeing your crankshaft, I must agree with Ozzie.
                      Bill O'Neal <br>
                      WCM
                      <a href="http://www.watercraftmagic.com"

                      Comment


                      • #12
                        Re: Crankshaft question

                        When you get your engine out, there are a few test you can do before you
                        tear it down.
                        You will need a dial indicator (screws into the top of you head), and
                        a degree wheel.
                        With the dial indicator installed in the number one, bring it up to TRUE
                        TDC, affix the degree wheel to the PTO (BACK) or MAG CUP (FRONT).
                        mark a reference point at zero.
                        Then move the dial indicator to the number 2, bring it to TDC and check
                        your degree wheel.
                        It should be EXCACTLY 180 Of your first, if it is off 2 - 3 degree's.
                        Get a rebuild, this will help you out before you tear into it.
                        Get the new one welded too, though most shops do this anyway.
                        Hope this helps, has saved me many times.
                        L8TR
                        Rudedog

                        Comment

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