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  1. #11
    sdlvx's Avatar
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    Quote Originally Posted by K447 View Post
    I suspect something other than the spark plug wires is changing as you repeat your crank tests. Battery voltage declining, CDI warming up internally, resistive ground connection self-heating, something.
    100% agree with this. shortening the plug wire is just a placebo, the time you take to cut it and put it back on allows something to cool or reset and for spark to come back again. Could be a messed up flywheel too.


  2. #12
    Quote Originally Posted by sdlvx View Post
    100% agree with this. shortening the plug wire is just a placebo, the time you take to cut it and put it back on allows something to cool or reset and for spark to come back again. Could be a messed up flywheel too.
    Any suggestions where to start the troubleshooting process? Thank you guys for your time with this.

  3. #13
    casey67's Avatar
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    Aren't there 2 ends to those plug wires ?

  4. #14
    Quote Originally Posted by casey67 View Post
    Aren't there 2 ends to those plug wires ?
    I believe they run inside the electrical box and have little coils or something on them.

  5. #15
    sdlvx's Avatar
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    Quote Originally Posted by Stealthjm83 View Post
    Any suggestions where to start the troubleshooting process? Thank you guys for your time with this.
    k447 has a great write up on what to test.
    http://greenhulk.net/forums/showthread.php?t=98103

  6. #16
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    It's odd that the lack of spark would change cylinders. Fuji engines use a wasted spark set up, so all 3 cyls fire at the same time. All the coils are wired in series, so if 1 was bad, the other 2 would still be fine.

    sdvx might be onto something with the flywheel. Sheared woodruff key., debris stuck between the magneto and flywheel? Possibly bad magneto?

    Consider getting 3 of the cheap in-line spark testers from Harbor freight. ($4 ea) and install them onto the plug wires. It will show you what is going on with what cyls are getting spark.

    You definitely need bigger jets installed when you get this spark issue sorted out.

  7. #17
    Quote Originally Posted by xlint89 View Post
    It's odd that the lack of spark would change cylinders. Fuji engines use a wasted spark set up, so all 3 cyls fire at the same time. All the coils are wired in series, so if 1 was bad, the other 2 would still be fine.

    sdvx might be onto something with the flywheel. Sheared woodruff key., debris stuck between the magneto and flywheel? Possibly bad magneto?

    Consider getting 3 of the cheap in-line spark testers from Harbor freight. ($4 ea) and install them onto the plug wires. It will show you what is going on with what cyls are getting spark.

    You definitely need bigger jets installed when you get this spark issue sorted out.
    Funny you mentioned the in-line spark tester, I just bough one made by Lisle today! I tested every cylinder today and I feel like the spark should've been waaaaay brighter than it was appearing to be in the view glass. I'm not sure how bright this particular one should be but the videos I've seen clearly show a very bright bulb illuminate with spark. Maybe I'll go get another brand and try it out.

  8. #18
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by Stealthjm83 View Post
    ... in-line spark tester, I just bought one ... Maybe I'll go get another ...
    It works better if you have three spark testers on the three spark plugs. Then you can see if the spark pattern is varying across the cylinders.

    Right now you are assuming that when you look at the spark for one cylinder, that cylinder’s spark pattern/strength stays consistent when you move the tester onto another cylinder.

    I have had a Polaris engine years ago that changed the spark pattern as it cranked. With all three testers flashing I was able to determine that the ignition system was losing sync with the engine. That was not a Fuji engine, but I was going in circles until I saw the spark pattern.

  9. #19
    Well then it is settled, I will try to find individual cheaper testers so I can do all 3 cylinders simultaneously.

  10. #20
    sdlvx's Avatar
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    The basic idea of how these ignition systems works is

    1. Flywheel spins around on the crankshaft
    2. Sensors on the flywheel are read by a stationary sensor on the crank case in the flywheel area
    3. When the sensor is tripped, it sends a signal to the CDI
    4. The CDI then has a brief delay (timing curve) based on RPMs before it sends the signal to the ignition coil
    5. The ignition coil sends the spark from the coil to the spark plug

    A regular Fuji fires all three ignition coils at the same time whenever the sensor is tripped. The flywheel must be aligned with the piston positions. If they're not, the signal for when to send the spark is wrong. I always thought it seemed like voodoo magic but once I understood how it works it's not that complex.

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