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    #1

    plug fouling

    Hello All,

    Well......I 3x checked evrything about my bike except cam timing. Well, actually I did check it 3x.......but that seems so long ago.

    My bike runs rich, and won't stay at idle. When I do rev it, it sometimes does not come back down. It fouls the plugs on all four. 8O

    Can cam timing cause this? I have set the points, static timing, and dynamic timing. They are all dead on the money. 8O

    So....... what can this be........?

    The only thing I can think of is cam timing.....but isn't this engine 79 GS 850 an interference engine. Meaning if cam timing is off, the whole engine goes BANG!!!!!!!!!! :twisted: Thanks
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    #2
    easy way is to check the compression If the reading is way off the cam timing could be off. Have you cleaned the carbs? I would recheck the float level

    Comment

      #3
      Why did you check your cam timing?

      Let me ask why you checked your cam timing to begin with? Did it already have problems? I once had a 79 GS1000E that would puff a bit of smoke upon start up, I also had a problem with running rich and fouling plugs. I hoped all the problem was was valve guide seals, and worn seats, I checked compression and it was low (105 psi), so I yanked the head, replaced the valve guide seals, ground the valve seats and put it all back together, just to have the exact same problem. If a bike's rings are shot it will have low compression and also run rich. I would check this. The other thing of course could be a problem in your carbs.
      Cam/Valve timing usually will cause the bike to pop or backfire at idle, I think the 750 is an interference engine, I know the 1000 is.

      Comment

        #4
        Originally posted by SqDancerLynn1
        easy way is to check the compression If the reading is way off the cam timing could be off. Have you cleaned the carbs? I would recheck the float level
        Yep I have cleaned the carbs, installed new gaskets/ o rings, played with the idle screw, airjet screw, fuel screw, checked float levels 5x.
        The bike runs graet above 2000 rpm, but occasionally it will rev thru the roof only to be brought down, by downshifting or by the kill switch.
        I did a top end rebuild but kept the rings ok within spec, and did not grind the valves. The bike ran great before all of this (tan plugs). I pulled the head because the previous owner srtipped the spark plug hole very badly.
        I haven't checked the valve clearances, but if they would be out then they woulf have to be all out across the board, don't you think?

        Comment

          #5
          Big negative on your last single valves do go.

          Comment

            #6
            Sounds like carbs to me, pilot circut, blocked air jet. Sometimes when carbs are cleaned some old crud gets lossened and when you restart it the crud gets lodged somewhere else. Happened to me one year, I had a broken pilot jet and had to remove and clean the carbs 5 times before I got every last brass shaving out of there. When crazy things happen below 2000 RPM you can usually bet it is the pilot circut, especially when it runs fine above that RPM. With the richness and fouling, I would start with all the air jets and air passage ways, a complete disassembly and soaking is required, for a proper rebuild.

            Dr. Dre

            Comment

              #7
              It sounds like you've been pretty thorough, but, it sounds like how it might behave if the choke were on. Have you checked the choke cable and adjustment? Maybe it's sticking or out of adjustment or there may be some other problem with the choke circuit.

              Comment

                #8
                Hello,

                I think I will check out the cam timing, I am willing to bet that the exhaust cam will be out a tooth or too. I believe that the valve timing is a bit retared, and in a way I guess that I am too.

                Anyways I won't be able to look at it this weekend........my wife believes that there are things in the world that are more important than getting a motorcycle back up and running. Well, back to domestic tranquility....cutting the lawn.....cleaning the house.....doing all of the things aound the house that I've been putting off.

                Back to bikes......if the cam timing is on the money I read a post in the old q+a about electical problems causing fouling on all four. Specifically electrical related to the signal generator and ignition modle.

                Comment

                  #9
                  Hello all,

                  I just realized :roll: that my bike 79 gs 850 does not have a signal generator or an ignition module. It has a points system. :roll: DUH!

                  I guess that I will recheck the cam timing. I am willing to bet that I am out 1 to 2 teeth on the exhaust cam.

                  I will let you know how it goes.

                  Once again thanks very much

                  p.s Anybody live out on Vancouver Island?

                  Comment

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