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  1. #1

    GP1200R Ltd - front cylinder misfire problem

    Hi guys,
    Have any of you come across this problem?
    #1 cylinder is only sparking 1/3 to 1/2 of the time.
    #2 & #3 are fine.
    I sent my CDI back to Advent. It was fine. So the problem isn't with it.
    I even tried a stock CDI.
    I've replaced the voltage regulator.
    I've replaced the stator.
    I've replaced the coils and leads.
    The only things left to replace are the flywheel and wiring looms.
    Could the distance between the flywheel and pickup cause this problem?
    (One line of thought I was given last night)

    Thanks, guys.


  2. #2
    Might be a dumb question but How are you testing for spark? If you are doing it through the plug maybe try a new plug.

  3. #3
    Hydrotoys's Avatar
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    Quote Originally Posted by John
    Might be a dumb question but How are you testing for spark?
    I was thinking this too.

    Also,
    Have you ever had a cracked snout on your current flywheel? If so, were the magnets ever inspected? This will cause spark issues.

    The pickup should be okay, IF THE OTHER 2 are firing good. It's only one pickup for all three cylinders.

    Has the stator had ANY, and I mean ANY scuffs, or dings on it or the epoxy around the windings? This too will cause issues.

    Battery ground is good?

    Ground wire from stator cover to head still intact.

    You ride in salt water by chance? If so, put some dielectric grease under the caps...just enough to grease them up. Sometimes the water will force it's way past the front of the seat, and dribble down on the front spark plug wire. Dielectric grease helps prevent salt water from providing an arc path to ground by keeping the salt water out of the cap.

  4. #4
    Thanks for the ideas, Mark.
    The crank is a genuine Yamaha which has been T&W.
    The engine has a crank snout support also.
    This engine was originally built by Mark Hahn so it has a few extra things like crank case cooling & crank snout support.
    The stator is brand new. I've just replaced the old one in case it was the problem.
    I'm using a PET DX2100 tach to monitor the RPM.
    And, yes, I've replaced the spark plugs numerous times.
    No salt water, I live in Las Vegas. The plug wires & caps are brand new Accel 8mm copper.
    I'm going to pull off the flywheel and inspect the 3 magnets on the flywheel tonight. I should have a spare flywheel kicking around so I'm going to fit it and see what happens.
    This sure is a weird problem.

  5. #5
    Hydrotoys's Avatar
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    Any luck yet?

  6. #6
    Not yet, Mark.
    I thought I had found the problem with the plug & wire setup which connects the CDI to the coils. It was fine on the trailer, but crapped out when I dropped into the lake.
    I took it out yesterday.
    I disconnected the PV cables to try something else.
    Engine runs fine up to 5600RPM (wasn't pulling as hard as normal though because of the weak spark) as soon as I manually open the PV's the engine dies away.
    Weird!!
    I closed down the High Speed adjuster to 1/4 in case it was a high speed bog - it did nothing. Tried it at 1 1/2 turns and no difference.
    I'm just about ready to part it out!
    The darn thing was running so well until it failed while competing at Jet Jam in Havasu.

    I'm going to swap out my entire electrical box with the one out of my brothers GPR tonight. I'm fortunate that Lake Mead NRA is just 1 mile down the road (less than 10 minutes to the launch area). I'll keep you updated.

  7. #7
    Moderator RX951's Avatar
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    have you checked the plug wire resistance on all 3 for comparison ?
    what about a faulty or weak coil ?

    #1
    k-ohms 6.1 ~ 14.3

    #2

    k-ohms 4.6 ~ 11.1

    #3

    k-ohms 3.3 ~ 8.2

    Ignition Coil resistance should be 3.5 ~ 4.7 k-ohms (B/W – Spark plug lead terminal)

    check all the wires that attach to that specific coil. There could be a small break inside one of the wires.......



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