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Spark plug evaluation PICTURES

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  • Spark plug evaluation PICTURES

    1988 johnson 140 looper
    Losing power at WOT and cylinder 3 spark plug has dry black coating all over. Notice the pics as if you were lookin at motor from back. The 2 on the left are cyl 2 and 4 and the two on the right are 1 and 3. Also cyl 4 spark plug the sleeve slides up and there is no gap. Not sure why it does that. Maybe the plug is bad. I checked compression and it was 1-125 2-125 3-122 4-130. I changed all ignition parts except the timer base. I think it has a misfire on 3 but cant pinpoint the cause. Second picture is cyl 4 and 3rd pic is cyl 3. Any suggestions??
    Attached Files


  • #2
    Re: Spark plug evaluation PICTURES

    the plug with no gap is certainly not right, when you say you replaced all the ignition parts, exactly what was replaced? as in coils, power pack and so on?

    Comment



    • #3
      Re: Spark plug evaluation PICTURES

      spark plug #4 is trash, replace it, or just replace all of em. The rest look OK to me, but the detail pic of #3 is not too clear.

      I bet if you get rid of that #4 faulty plug your problems will go away.

      Comment



      • #4
        Re: Spark plug evaluation PICTURES

        I replaced stator, ppack, coils, wires, plugs. It doesnt matter if I put a brand new plug in cyl3 it will always come out looking like that (black dry soot). I know that cyl has a problem but cant figure out what it is. The plug with no gap is wierd it seems like any plug I put in there seems to come out like that even if it is gapped before, but maybe Im wrong. Maybe just the sleeve is loose on that plug. I think the problem is cyl 3 becauze no matter what I do that plug always always always looks like that.

        Comment



        • #5
          Re: Spark plug evaluation PICTURES

          Originally posted by mbecke2 View Post
          The plug with no gap is wierd it seems like any plug I put in there seems to come out like that even if it is gapped before, but maybe Im wrong.
          Piston is hitting the plug(bad rod bearing)
          Life member of POTSOS,
          "Preservation of Old Two Stroke Outboard Society"

          Comment



          • #6
            Re: Spark plug evaluation PICTURES

            Under what conditions was the engine run when you pulled the plugs. Unless you make a long wide open throttle run and then immediately chop the throttle and pull the plugs to read them you will never get a good reading. Idling for long periods on a two stroke can mess up the plugs. It would appear that the engine is running very rich so you likely don't have an ignition problem but rather a carburetion problem. As for the plug with no gap, of course something is wrong on that cylinder. Look into the spark plug hole with the piston at top dead center. I think you will see a mark on the piston where it has been hitting the plug.

            Comment



            • #7
              Re: Spark plug evaluation PICTURES

              Maybe the cylinder is full of carbon???

              Comment



              • #8
                Re: Spark plug evaluation PICTURES

                Seems like some strong compression numbers on that engine. Any chance the heads have been cut or replaced?

                Comment



                • #9
                  Re: Spark plug evaluation PICTURES

                  I seriously doubt there is anything wrong with the plug that is closed, there is something going on that is closing it up, bearings would be very noisey if they were that bad, I reckon you would hear it easily, more like the head has been machined and it is now too close, or the wrong heads are fitted, you need to fix that problem long before you worry about a cylinder running rich! trust me on that one. It may be possible to perhaps fit a couple of extra washers under the plug to space it out a bit, but it is not fixing it, just covering the problem.

                  Comment



                  • #10
                    Re: Spark plug evaluation PICTURES

                    The no gap plug is defective, the insulator has broken, discard immediately.
                    sigpicSignature- If you have fuel and spark- Have you checked compression?

                    Comment



                    • #11
                      Re: Spark plug evaluation PICTURES

                      I'm with bktheking, center electrode insulator has broken and slid up. If something hit the negative electrode it would be bent down toward the center electrode but it looks the same as others. Would still replace it though.

                      Comment



                      • #12
                        Re: Spark plug evaluation PICTURES

                        He said every plug put in that cylinder ends up gap closed.
                        Look at piston top I bet there is some intication of the piston striking the plug.
                        If the bearing is that bad I think if you rock the motor with the piston in mid stroke
                        you may here the bearing.Or with a screwdriver on the piston you may note a lag in its movment.

                        Comment



                        • #13
                          Re: Spark plug evaluation PICTURES

                          Then if that's the case yes bad bearing or wristpin.
                          sigpicSignature- If you have fuel and spark- Have you checked compression?

                          Comment



                          • #14
                            Re: Spark plug evaluation PICTURES

                            Thanks for all the replies. I bought the motor couple years ago so Im not sure about the history- redoing heads, pistons etc. But anyway I'm goin to replace all the plugs and post back. I think the piston maybe hittin the plug as this makes since to me. I will take a look and post update. Again thanks.

                            Comment



                            • #15
                              Re: Spark plug evaluation PICTURES

                              This is a 140 looper....there is no way for the piston to hit the plug...the plug does not extend into the combustion chamber, the chamber is sort of a hemisphere, and the piston is a relatively flat top. It is not like a crossflow which has part of the piston extending into the combustion chamber.

                              Are you sure you are using the right plug? Should be Champion QL77JC4.

                              If you have the wrong plug...threaded part too long...it may reach down far enough to hit...but it is a long way, at least 3/4".

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