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  1. #1
    butterbean_29512's Avatar
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    2001 GPR no power from rear cylinder

    Hello all...I've got a 2001 GPR that blew the rear cylinder. (Customer's ski). Its back together, rear cylinder isn't making power. Swapped the coil with a known good coil, plug wire, and good plug. When you remove the plug wire from the plug and ground it on the plug for testing while in the water it is obviously breaking up. Check with a spark tester and shows a good hot spark, pull the plug and ground the plug out, and shows fire. I'm at a loss. Anyone experienced this problem before? I'm almost ready to pull my hair out! Lol! But seriously...anyone got any suggestions on what to try next?

  2. #2
    steve45's Avatar
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    What makes you think it's an ignition problem?

    If it blew the cylinder, it may be running very lean.

  3. #3
    jeffg426690's Avatar
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    Hey Jack - long time...!
    Q: when you pull the plug and connect ign wire to plug and ground it while cranking, are you doing that in the water? Thinking of possible difference that is showing up when the crank has a load on it? Might point back to the stator?


  4. #4

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    This is a unique situation for sure. I’m anxious to see what the cause is.

  5. #5
    butterbean_29512's Avatar
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    It is certainly unique. Gonna swap out the ECU with a known good one just to be sure. When you crank it the plug is wet, it just makes no power. If the ecu isn't bad then I'll pull the engine and start over. This one is whipping me for sure. I haven't ruled out a very lean condition, but if that's what it is its too lean to run on that cylinder, because it makes zero power on that one. BTW...carbs rebuilt to the recipe for success, so carbs are fresh. It idles well on the trailer....but they all do, don't they??? Lol.

  6. #6

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    Just a crazy thought…. Could the crank phase be that far off to cause this issue??

  7. #7
    Myself's Avatar
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    Spark plugs can fire just fine out laying next to a ground and still be bad. Ohm them from connecting tip to the hex, if they read any ohms they are bad and the spark shorts to ground when the plug is installed.
    Triples will start and run on any ONE cylinder if the engine is warm. Try running only one cylinder at a time. If the one cylinder doesn't run....pull the plug, squirt a bit of fogging oil in it and try again. If it's a spark issue it will still NOT run. If it's a fuel issue it will light right off and try to run....if only for a couple seconds.
    I did a set of GPR carbs last year that had a pass through nipple so corroded up I had to heat the aluminum and pull the brass nipple out. Then carefully scrape away all the corrosion and ream the passage. Then tap the brass nipple back in with a bit of red loc-tite. Alwaya check the passages with with a bit of air before reassembly.

  8. #8
    butterbean_29512's Avatar
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    After swapping coils, plugs, and ecu's, found out its a fuel issue. Have not had time to dig back into it, but will.

  9. #9
    butterbean_29512's Avatar
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    Just to update on the problem...checked fuel, and tore motor back down and replaced rear seals just to be sure. Put it back together, still same problem. So, after swapping coils, wires, ecu, checking rear seals just in case....turned out the crank is out of phase. The owner is deciding what to do with it....but it'll probably be repaired. The ski is in great condition. The engine had water in the rear cylinder when I received it, I guess I should have suspected crank phase a little earlier in the troubleshooting process.

  10. #10

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    What do I win????

    HA!!! Just kidding, glad you figured it out.


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