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Spark Plugs- 1985 XJ 700 Maxim

Discussion in 'XJ Technical Chat' started by Kingston, Dec 14, 2011.

  1. Kingston

    Kingston New Member

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    I want to change plugs on my 1985 XJ 700 Maxim. The plugs in there now are Champion RN7YC and they seem to run fine, but old. Could someone let me know what the manual calls for, as I don't have a owner's manual.
     
    Kingston, Dec 14, 2011
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  2. smurf667

    smurf667 Member

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    NGK BP8ES or equivelent with a gap of 0.7~0.8mm (0.028~0.031in)
     
    smurf667, Dec 14, 2011
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  3. Kingston

    Kingston New Member

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    Kingston, Dec 14, 2011
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  4. Kazzk

    Kazzk New Member

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    I got a set of 4 NGK DR8EIX iridiums for my X and was very happy with them.
     
    Kazzk, Dec 14, 2011
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  5. Kazzk

    Kazzk New Member

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    Sigh.. Sorry. There are more differences between the air cooled and X model than I thought. For some reason I expected them to share the same 20 valve engine and would share spark plugs. I guess iridiums are not available in that size.
     
    Kazzk, Dec 14, 2011
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  6. Kingston

    Kingston New Member

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    I think that Sparkplugs.com was wrong in saying can use NGK BPR6ES as I think it's too hot. I'm going to go with NGK BPR8ES or Champion RN7YC.
     
    Kingston, Dec 14, 2011
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  7. smurf667

    smurf667 Member

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    NGK BPR8ES is what it says in the service manuel for the XJ700 which is what I looked at for you, don't panic, I wasn't looking at the service manuel for my bike, which is the 700 X 20 valve version lol
     
    smurf667, Dec 14, 2011
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  8. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    They don't, and that's the big difference between the "X" models and the earlier-generation (8 valve) air-cooled motors. Besides the liquid cooling of course.
     
    bigfitz52, Dec 14, 2011
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  9. tskaz

    tskaz Active Member

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    I would have to agree. You shouldn't even need the 7s if it's cleaned and tuned properly.
     
    tskaz, Dec 14, 2011
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  10. RickCoMatic

    RickCoMatic Well-Known Member

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    RickCoMatic, Dec 14, 2011
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  11. KumanK

    KumanK Member

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    Correct me if im wrong, but arent you not supposed to run resistor plugs on these bikes unless the coils have some kind of resistor? Which would mean all the NGK BPR would be the wrong plug?
     
    KumanK, Dec 18, 2011
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  12. parts

    parts Member

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    NGK BP8ES- not BPR8ES-that's a resistor plug and not needed for
    our 700.
    BTW-I've run the ngk's without any issues.
     
    parts, Dec 18, 2011
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  13. smurf667

    smurf667 Member

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    I stand corrected, it is indeed the NGK BP8ES that your bike requires and not the NGK BPR8ES as I stated earlier. In fact I don't know what made me put that, as I had said the correct one in my first post.
     
    smurf667, Dec 18, 2011
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  14. HirsuitHeathen

    HirsuitHeathen Member

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    How compatible are XJ700 parts with an XJ750's? I'm talking motor, electrical system, carbs etc.
     
    HirsuitHeathen, Dec 18, 2011
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  15. RickCoMatic

    RickCoMatic Well-Known Member

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    The industry floods the market with Resistor Plugs.
    With Solid State devices sensitive to RF becoming a way of life; non-resistor Spark Plugs are becoming increasingly harder to find.

    The Manufacturers are moving-away from the basic Spark Plug; offering a full-line of Plugs made with various precious metals in designs which they say offer higher performances for just a few dollars more.

    In some cases, vehicle manufacturing has changed to adopt to the newer Plugs; with Spark Plug Holes made for the smaller diameter with longer reach Plugs.

    Champion had to adjust to the new tech to be able to say they are he Spark Plug of Formula-1. Although, they can't say: "The same Plugs we sell for use in your car", any more.

    The Champion F-1 Plug is manufactured to WEIGH far less than the Old Standard; and cost Race Teams $50. to $60 bucks a Plug.

    What Plug should you buy for your Bike?

    That depends upon what condition and in what state of Fine Tuning your Engine is in.

    If you are a Tweaker who has got their Bike right on the hairy-edge of the Fine-tuning capable for these Plants; with no serious Oil Consumption issue to foul the Plug, ... you can spend a lot of money for Plugs and a decal to stick-on the bike.

    The opposite end of that situation might dictate you should run a couple of different Plugs.
    In Holes that you know tend to Foul the Plug and start missing; you can run a "Hotter Plug" to prevent fouling or extend the interval before it does get fouled.

    http://www.caranddriver.com/columns/tec ... -in-toledo
     
    RickCoMatic, Dec 18, 2011
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  16. parts

    parts Member

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    The diff (besides body style) is the stroke has been shorten on the 700.
    Bore remains the same. I think the 750 cams may have a slightly higher lift.
    The 700 uses hitachi 33mm and the 750 hitachi 32mm carbs.

    Otherwise it's pretty much the same power plant-maybe someone else can
    chime in if I missed something.

    As far as elect. your guess is as good as mine (lol)
     
    parts, Dec 19, 2011
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  17. HirsuitHeathen

    HirsuitHeathen Member

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    Alright thanks for the info. I wonder why they made the carbs one mm smaller? Anyway the eBay listing I was looking at ended and it's a good thing I came here first. Sorry for slightly derailing this thread.
     
    HirsuitHeathen, Dec 19, 2011
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  18. tabaka45

    tabaka45 Well-Known Member

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    My owner’s manual states BPR8ES (NGK) or W24EPR-U (Nippon Denso). So I guess resistor plugs are correct. I’m darn confused over all the alternatives.
     
    tabaka45, May 28, 2018
    #18

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