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spark plugs

Discussion in 'XJ Technical Chat' started by oscarcat, Feb 9, 2019.

  1. oscarcat

    oscarcat New Member

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    hi all. just wondering the difference between bp7es and ones in my bike bpR7es thanks
     
    oscarcat, Feb 9, 2019
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  2. XJ550H

    XJ550H Well-Known Member Premium Member

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    The R means it is a resistor plug. it slows down the discharge. increases the duration of spark


    also reduces the RFI suppresses the noise
     
    Last edited: Feb 9, 2019
    XJ550H, Feb 9, 2019
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  3. Timbox

    Timbox Well-Known Member

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    First off welcome to the forum, so much info here to read and soak up. Lots of people with great info and ideas.

    I think the "R" is for a resistor. "This spark plug has resistor that is produced with a glass and carbon mixture" The other has no resistor.
     
    Timbox, Feb 9, 2019
    #3
  4. k-moe

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

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    Why the resistor matters:
    Yamaha(and most other motorcycles at the time) used resistive spark plug caps. If you use a resistive plug with a resistor plug cap you will be adding resistance to the system, and making cold starts more difficult (along with the potential for poor performance under all conditions).
     
    k-moe, Feb 9, 2019
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  5. oscarcat

    oscarcat New Member

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    hi k moe that would sound about right thanks gets pretty cold and damp here im scotland. my bike does not like the rain sounds like its running on 2 cylinders. have waited till dark to check coils and leads, no sign of cracks. thanks man
     
    oscarcat, Feb 10, 2019
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  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    what bike are you talking about? if the plug caps are resistive and correct there is no need to have the resistor plugs.
     
    XJ550H, Feb 10, 2019
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