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  1. #1

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    What do these spark plugs tell you? Missing above 7krpm

    2003 Seadoo GTX 1600cc supercharged forged jet ski. Forged Darton MID block, Darton piston sleeves, CP forged pistons, Rotax ECU, Malpassi FPR, custom camshaft, 50psi(?) injectors, external intercooler, HKS SSQV BOV.

    Ski is missing above 7000rpm.

    Anything to 6900 is smooth, as soon as it touch 7000 it drops back down to around 6300 and runs rough until I back off the throttle.

    Has only started happening over the last month. Has been GPS'd at 80mph years ago.

    I have a couple of ideas but I want to hear from someone else
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  2. #2
    speedskixp's Avatar
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    Just a guess. Leaky riva IC. Are you running a riva IC?

  3. #3
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    Lean...

  4. #4
    it looks like overheated just a guess though

  5. #5
    Nothin' better than Doo'in it! BigDaddyRXP's Avatar
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    A set of EGT's and a A/F meter will tell you everything! Two of those plugs show detonation

  6. #6

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    Quote Originally Posted by speedskixp View Post
    Just a guess. Leaky riva IC. Are you running a riva IC?
    If I was losing air pressure somewhere through the IC piping wouldn't it then run rich?

    Quote Originally Posted by Danny View Post
    Lean...
    I have CRS's old ski, after making this thread I've been reading back on his posts...

    http://greenhulk.net/forums/showthread.php?t=5046

    Quote Originally Posted by CRS View Post
    John, the denso`s were causing a hgh speed misfire. Not realy bad but enough cost about 250-300 rpm.The combination of the plugs,the mixtures being to rich and some poor conections in the ECU plug added up to about a 1000rpm loss. The improvement going back to regular plugs was immediatly noticable even though the misfire with denso`s was barely noticeable with all the wind noise etc that you get at 65mph. Hope this helps.
    Are the Denso's really that bad?

    The plugs are actually brand new, less than 1 hour old... I can't say it was running fine on the previous set of plugs (NGK), as I was chasing a P0351 code, which is a different story altogether.

  7. #7
    Nothin' better than Doo'in it! BigDaddyRXP's Avatar
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    Quote Originally Posted by OSiRiSNZ View Post
    If I was losing air pressure somewhere through the IC piping wouldn't it then run rich?
    Water leak

  8. #8
    speedskixp's Avatar
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    Quote Originally Posted by OSiRiSNZ View Post
    If I was losing air pressure somewhere through the IC piping wouldn't it then run rich?
    Not air. Water! If your ic is leaking water into the intake it will miss at high rpms and can leave your plugs with little pits in them like they appear from the pics. You need to pressure test your IC.

  9. #9
    formerly Gold06RXP Turbo Nick's Avatar
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    I dont see any sign of detonation. If that where the case there would be specs of aluminum on the porcelin above the electrode. There isent any. I would try a set of OE plugs and see if it helps
    Quote Originally Posted by bigdaddyRXP View Post
    A set of EGT's and a A/F meter will tell you everything! Two of those plugs show detonation

  10. #10

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    Quote Originally Posted by GOLD06RXP View Post
    I dont see any sign of detonation. If that where the case there would be specs of aluminum on the porcelin above the electrode. There isent any. I would try a set of OE plugs and see if it helps
    What exactly are the OE plugs?

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