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  1. #1
    Bryan K's Avatar
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    Which spark plugs with 1390 big bore??

    Just got an 01 1200 GPR with the 1390 big bore kit and stock heads milled down for 145 psi compression. Just wondering if I should run the stock plugs or what?


  2. #2
    Flying Scotsman's Avatar
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    I would say no,higher compression.

  3. #3
    My son (mohawk man) jeffsntx's Avatar
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    Bryan, I would think you would be fine with the stock heat range plug. The compression is not high enough to need a cooler plug.

  4. #4

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    9

    Cool

    go 9
    later cd

  5. #5
    Flying Scotsman's Avatar
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    Yep.........

  6. #6
    GPR114's Avatar
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    8's should be fine with 145 lbs. Read your plugs? Lowell has a great chart for plug reading.

  7. #7
    My son (mohawk man) jeffsntx's Avatar
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    I am running 8's on a 145 PSI non big bore and they are fine. I run 9's in my project and we wont discuss the compression on it. I need to order some domes to get it in a REASONABLE range.

  8. #8
    Happily Self-Employed WFO's Avatar
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    Quote Originally Posted by GPR114 View Post
    8's should be fine with 145 lbs. Read your plugs? Lowell has a great chart for plug reading.
    Quote Originally Posted by jeffsntx View Post
    I am running 8's on a 145 PSI non big bore and they are fine. I run 9's in my project and we wont discuss the compression on it. I need to order some domes to get it in a REASONABLE range.
    I say BR8ES too.

    The 9s are colder and may foul with extended idling periods.

  9. #9
    2000 GPRXP 4tec shooter98xpl's Avatar
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    On my 1600 big bore triple piper I run BR8ES-11's.
    SHOOTER

  10. #10

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    9

    Cool

    you'll get better plug readings with 9 (were only talking 1 heat range here 8 are fine BUT you'll get better color with 9) and if everything setup right you should not load up! if so 1 plip and gone

    later cd

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