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  1. #1

    GPR cylinder not firing...??

    hey guys so i just had the ski out on the lake for the first time this year and i have a problem. when you punch the throttle the ski will sometimes bog, then will eventually pick up rpm's. but no matter what, the ski tops out at 6000 rpm's, and about 45 mph. BUT, in the driveway she will rev right up to redline. when i took her off last year she was pulling great top end..around 60-63 mph.

    i just pulled the plugs as soon as i got home. two of them look good and look like they have been firing fine. the other plug (#1 cylinder) looks like it hasnt been fired at all. its very clean and just has fuel/oil residue on it.could this be the cause of my missing 1000 rpm's and 15 mph? what could be the cause of it not firing. its getting fuel and oil. bad spark plug wire?

    i did all of the mods in my sig over the winter with the exception of the d-plate and chip.

    other info..
    the first run i made yesterday was with a 13/19 prop. i thought that maybe my motor couldnt spin it, so i swapped out to the stock prop and its still having a problem. then i discovered the issue with the plugs.
    the ski starts up and idles in the water and driveway just fine. my mods are in my sig. i havent messed with the carbs at all. ski has 77 hours on it. compression is 105-110 across the board.
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  2. #2
    Mike's GPR's Avatar
    Join Date
    Mar 2008
    Carol Stream, IL
    Maybe a bad wire, bad plug, are all you oil lines OK and still attached? I'm not exactly sure, I'm sure someone will tune in with better advise soon.

  3. #3
    If your not doing something, its hard to screw up. stlouisramsfan's Avatar
    Join Date
    Jul 2007
    Pontoon Beach Illinois
    Have you checked for spark ie pulling and grounding the plug to see what's happening...

  4. #4
    kham383's Avatar
    Join Date
    Jun 2008
    Gold Coast Australia
    It's more than likely a bad lead or coil. check the resistance on your lead with a multimeter if that's all good then check the coil the resistance values are in the manual under electrical analysis.

  5. #5
    oil lines are all good. i clamped them with hose clamps a few weeks ago to prevent them from popping off.

    havent checked for spark yet. i would have this morning but i am the best man in a wedding today and i dont have time lol.

    i will check the resistance asap. where exactly is the coil? and is this a common prob with bad wires or a bad coil?

    so do you guys think this is the problem? to me the clean plug indicates it hasnt been fired, and leads me to believe that is the root of my missing rpm's. would you guys agree? would the ski run on two cylinders without making much fuss? i dont know 2 strokes, but when a car is missing a cylinder you will know it. thank you for all your help and i will keep you all updated. please let me know if you have any other ideas. caolan

  6. #6


    On the oil lines they are talking about you cant put a clamp on them only zip tie or small otiker clamp.second check your compression,if all is well check your spark on all 3 cylinders,thenif no spark change plug first,then ohm wire ,cap and coil,by then you will probably have found your problem,did you plug all wires back in after installing d-ring,I know you installed resistor to take place of o2 sensor>Marvin

  7. #7
    Haven't fallen yet. MJE's Avatar
    Join Date
    May 2007
    Buzzards Bay, Massachusetts
    wire lead has a bad connection on that particular wire to boot transition imo.

  8. #8
    hey so i replaced the plug first just in case it was bad... checked it on the trailer and it was firing a nice blue spark. took it to the lake and it took off great out of the hole for a second, then the power loss came back. BUT, this time it would intermittenly have power here and there... i noticed it when i would stop then punch the throttle that it would actually rev up and pull hard for a second, then lose power again. it would do this maybe one out of 15 times. the other 14 it would just bog like usual.

    heres the weird part, i checked the resistance on the wires. i got 1.8k ohms, 1.6k ohms, and 1.4k ohms on cylinders 1, 2, and 3 respectiviely. (cyl 1 is the bad cylinder). it should be ALOT higher on all 3 wires per the manual. i triple checked the settings on my tester and did the test 3 times on each lead. THEN, i checked all 3 coil packs, and i got 1.3k ohms on all of them. that should be alot higher too...between 3.5k and 6k on the secondary terminal. im lost here because now i have no idea what to replace. my tester is reading 2.4k ohms when its touching nothing, and when you touch the leads together it goes to 0. dunno if this explains anything.

    the only only other thing i could see was that there was a little bit of black stuff on the plug wire lead where it contacts the plug. i scraped it off. maybe that was the cause of the intermittent power gain/loss? im totally at a loss. i would replace the coil pack and wire but the pack is 90 bucks and the wire is another 80! i dont wanna waste oney unless i know what the prob is. you guys have any thoughts? thanks in advance!

  9. #9
    All hail the Chief! fullboogie's Avatar
    Join Date
    Nov 2005
    It ain't the wires, and having lower resistance isn't bad. Sounds like you may have either a coil going bad or a CDI going bad (if it's carbed)

  10. #10
    WATER WOODY's Avatar
    Join Date
    Aug 2005
    Minden, Nevada, United States
    Im with Fullboogie....change out the CDI unit first before spending money on parts you dont need.Next thing to check is this

    Do you know someone who has a 00'-02' GPR that you can swap CDI units out to test?

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