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  1. #1
    IDoSeaDoo's Avatar
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    Modified 787 going lean when I turn the water on

    Building a modified 787 for the first time. Running Factory Pipe Spec 1, NOVI 42i modified stock carbs with 162.5 mains, 77.5 pilot, 2.0 n/s and black spring (around 18psi popoff), no choke plates and R&D power plenum FA. MSD water injection with no jet to the spray bar, 125 to mid pipe and 145 to water box. The thing fires up and runs pretty well until I turn the hose on. Then the RPMs increase until it develops a lean run-away condition. I open the throttle and shut it off. My flywheel spun off after a few times starting it up. I had it torqued down to 82 ft lbs as the book said. It still spun off. Could it have been my loose flywheel giving that lean condition, or was it how I have my pipe setup? The lean condition starts as soon as I turn on the water.


  2. #2
    IDoSeaDoo's Avatar
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    Confirmed the issue doesn't happen when the house is off. This is my first time trying to tune with an after market pipe.

  3. #3

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    Bad crank seals can cause a lean out but I don't think this can happen from the flywheel spinning off. My guess would be something to do with the pipe water jetting/routing

  4. #4
    Tool Bag water worx's Avatar
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    On a 800 if the flywheel "spun off" then the rear crank seal would be leaking causing a lean condition. Use loctite on threads & let dry 24 hours & then put ski in wtaer & drive. You cant "tune" on the hose.

  5. #5

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    Water works is right, couldn't remember if the pto went into the seal, it does.

  6. #6
    IDoSeaDoo's Avatar
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    Yes, I applied loctite to flywheel and returned. There is a new seal there. Before it spun off, I did a pressure test and it passed. Last night I was testing. It only does the lean run away if the head pipe hose is not pinched. I didn't have a jet in there, just solenoid and running quarter inch hose right to head pipe. Pinch that off, and it revs up normally and comes back down. Release, and it runs away. The MSD pulse width water controller's green light would sometimes go out. That normal?

  7. #7

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    The lean run away can be caused by carbs out of balance.

  8. #8
    Hurricane1000's Avatar
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    Could also be from the idle being set too high......

  9. #9
    IDoSeaDoo's Avatar
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    I think that may have been part of the problem. It's been years since I've run a 787. I think I had my TTO tach set to 2 pulses per revolution, so I think it was giving me the wrong signal. I set it to 1 pulse per rev, and brought the RPMs down to 3000, and it sounds a lot more tame now. Also doesn't rev out. But I also added a 125 jet just before the head pipe ECWI solenoid. So now, that's getting a LOT less water. Strangely, the MSD water controller green light seems to go on only when the RPMs get up to where it's supposed to do something. Does the green light stay on only when that thing is activating the solenoid, or should it stay on all the time?

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