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Spark plugs

Discussion in 'XJ Technical Chat' started by Madmur, May 1, 2009.

  1. Madmur

    Madmur New Member

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    So i bought some spark plugs for my bike today. Hanyes manual recommends NGK BP7ES for the XJ750 seca. I pulled the ones from my bike and they were NGK BPR7ES. A quick Google search & I find out the added R is for resistor type plugs. A previous owner has changed the wires & I don't believe they have resistor caps. They are just soft rubber. So my question is... Does it make a difference if the resistor is in the cap or the plug? & What is the purpose of this resistor?
     
    Madmur, May 1, 2009
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  2. rotaryboots

    rotaryboots New Member

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    Resistor plugs cut down on radio interference for the most part. there's not a whole lot of difference between the two types besides that. In my opinion it would be best to keep the system resistored wether it be in the cap or the plug.
     
    rotaryboots, May 1, 2009
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  3. Ace_Frehley

    Ace_Frehley Member

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    That's my understanding of it too. Either resistor plugs or resistor caps. Although, I ran both resistor plugs and caps for a season with no noticeable difference.
     
    Ace_Frehley, May 1, 2009
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  4. SQLGuy

    SQLGuy Well-Known Member

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    The resistors are also there to set burn time. More resistance = longer burning, but less intense, spark.

    If the coils are original, the total resistance, whether in the plugs, caps, or combination of both, should be kept close to stock (5K per cylinder, I believe).
     
    SQLGuy, May 1, 2009
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  5. Madmur

    Madmur New Member

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    Thanks guys, looks like I'll take those plugs back and get the R type.
     
    Madmur, May 2, 2009
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