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550 random knock

Discussion in 'Hangout Lounge' started by designerjer, Jun 24, 2014.

  1. designerjer

    designerjer Member

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    My 81 XJ 550 seca is making a random knock at lower idle. Does not occur yet while clutch is pulled in. Seems to be no real pattern to it. However it really seems to be coming from the right lower side of the engine. Bike runs fine. It is not clutch chatter, I know that feeling and sound. It sounds about like a screw driver tapping the case and is not consistent. cruising through my neighborhood at 25 mph it happens once then 3 times then 2 etc. Sounds like metal hitting metal but not real loud, just enough to hear it and barely feel it. I don't hear it going faster. But everything is loud then. It does not seem consistent with road bumps so I don't think it's loose parts. Pulling in the clutch and coasting seems to stop it. Then engage the engine and it will happen again intermittently. The sound just started to be noticeable.
    No idea on the mileage of the motor. I have had a lot of crank case smoke out the vent filter but just directed it under the pods and seems to be fairly decent now. However the red oil on the K&N pod filters keeps breaking down fast and losing its red color as a result. I imagine it is due to the crank case fumes passing through it.

    Any help on what the knocking may be?
     
    designerjer, Jun 24, 2014
    #1
  2. Brothastonebones

    Brothastonebones New Member

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    Has the clutch been tinkered with lately?
     
    Brothastonebones, Jun 24, 2014
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  3. designerjer

    designerjer Member

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    I have not messed with the clutch before
     
    designerjer, Jun 24, 2014
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  4. designerjer

    designerjer Member

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    I will try syncing the carbs again. Maybe it is some small back firing? I also went through and tightened the header bolts. Some were a little lose.
     
    designerjer, Jun 25, 2014
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  5. FtUp

    FtUp Well-Known Member

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    sounds like possibly a plastic chunk of a chain guide bouncing around. just a guess though.

    CN
     
    FtUp, Jun 25, 2014
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  6. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    The 550 doesn't have the plastic chain guide that disintegrates like in the shaft-driven bikes. The 550's primary chain is a "true" primary in that it drives the transmission; and as such it has an hydraulically-operated chain tensioner that works on engine oil pressure. Completely different design than the stationary guide that likes to break into hunks.

    Adjust the cam chain if you haven't already;

    and if it for sure is coming from the "lower right" then it would be a very good idea to pop the clutch cover off and have a look.
     
    bigfitz52, Jun 25, 2014
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