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Misfiring bore washing

Discussion in 'XJ Technical Chat' started by yamahaha, Oct 14, 2016.

  1. yamahaha

    yamahaha Member

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    My 81 xj 750 is only running on three cylinders and back firing a little. More like a choof than a backfire but I poke my nose in the crankcase and smell the oil and all I can smell is petrol. Fuel not getting burnt on one or more pots? New plugs installed today and still no joy. I have no idea about rectifiers or igniter boxes but could this be the next place to look?
     
    yamahaha, Oct 14, 2016
    #1
  2. XJ550H

    XJ550H Well-Known Member Premium Member

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    ohm out your plug caps you could have a bad cap

    it sounds like you have a leak in one or more of your carbs filling your crank case with gas.? sticking float or needle valve not sealing
    have you checked the fuel height.?
    done the church of clean with the carbs?

    when you try to start it look at the cylinder that is not firing and see if the plug is wet.

    reverse the spark plug wires from the same coil set on your misfiring cylindersee if the problem moves to the other cylinder
     
    XJ550H, Oct 14, 2016
    #2
  3. cgutz

    cgutz Well-Known Member

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    Been there - had that happen, replaced with new spark plug cap and wow!
     
    cgutz, Oct 14, 2016
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