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Firing is alternating between cylinder #3 and #4

Discussion in 'XJ Technical Chat' started by Marco Gambino, Jul 9, 2022.

  1. Marco Gambino

    Marco Gambino New Member

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    Hello guys,
    I'm new here and I have a problem with my '97 XJ600 Diversion. Basically what title says, it usually doesn't fire on cylinder #4 but it randomly starts firing on it sometimes, however when that happens it stops firing on #3. Plugs and coils are all good, carburetors have been cleaned and sync'd, valves however haven't been touched in years and the pressure in cylinders is pretty low at a bit less than 1 MPa.
    Any ideas on what might be wrong? Ideally I'd like to avoid doing big repairs in hope of randomly fixing the problem, rather I'd identify it specifically at minimum cost as I suspect I won't be riding much this year.
     
    Marco Gambino, Jul 9, 2022
    #1
  2. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    First confirm that the plug wires are connected to the correct cylinders.
    Then start the bike in the dark to check for shorts to ground at the spark plug wires and coil bodies.
     
    k-moe, Jul 9, 2022
    #2
  3. Andrew Nichols

    Andrew Nichols Active Member

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    Clean the contacts from the TCI to the coils and check the connection between the spark plug wire and the plug cap.
     
    Andrew Nichols, Jul 10, 2022
    #3
  4. Marco Gambino

    Marco Gambino New Member

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    Thanks for your replies. I finally had some time to pull out the bike and it turns out I was wrong. The firing doesn't switch randomly from one cylinder to another. #4 doesn't fire with choke on and #3 doesn't fire without choke. So I'll have to play with the fuel mix screws. Hopefully I can find on the web what the best setting is.
     
    Marco Gambino, Jul 15, 2022
    #4

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