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  1. #1

    runs on trailer, but bogs in water

    Got my 96 Sl780 started last weekend, started it a few times to burn the storage oil out of the cylinders, starts but bogs in the water at mid range, my son tells me it was doing the same thing last fall before we stored it for the winter. I checked the compression and all three are even-135. It will not run on any one cylinder, but will run on two. When I do get it going it still smokes a fair bit, with smoke and heavy fuel mixture coming from the PTO carb.

    Any ideas on what to try next. The machine was rebuilt in 1995, a new starter last year and had the carbs cleaned at that time, it ran great all summer except for the bogging late last season.


    Ekmols


  2. #2
    ripcuda's Avatar
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    Could it be a tank of bad gas from late last season still giving you issues? Seafoam is great stuff to dry out gas and clean the fuel system and for storage. I use it in all my machines.
    Did you check/drain the fuel/water separator? Might have water in it from bad batch of gas. Drain it and refill with clean gas and re-install.
    Plugs look good?
    Have you peaked with a flashlight/borescope into the cylinders through spark plug hole to see how the tops of the pistons look regarding their color. It's the best way to read if that cylinder is running lean or rich based on what you see.
    Check your fuel filter.
    It does sound like somethings gummed up in your carbs though... I know you said they were cleaned last year. I'd be real careful about "getting on it" until you get it sorted. That's the fastest way to kill an engine.

    Good luck

  3. #3
    The carbs have been off twice now and checked by a mechanic, the oil injector was stuck wide open, sounded good on the trailer, but bogged when in the water, put in new plugs, again, sounded great on the trailer, good rev's. but again bogged when put in the water. I am stumped. Mechanic wants to phase the crank, could that be the problem?

  4. #4
    I am having the same problem I'm down to stator or cdi

  5. #5
    BlueFishCrisis's Avatar
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    Quote Originally Posted by ekmols View Post
    The carbs have been off twice now and checked by a mechanic, the oil injector was stuck wide open, sounded good on the trailer, but bogged when in the water, put in new plugs, again, sounded great on the trailer, good rev's. but again bogged when put in the water. I am stumped. Mechanic wants to phase the crank, could that be the problem?
    What are the high and low speed needles set at? Have they been returned to factory settings? What jetting is currently in the carbs? How do they compare to factory?

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by ekmols View Post
    Got my 96 Sl780 started last weekend, started it a few times to burn the storage oil out of the cylinders, starts but bogs in the water at mid range, my son tells me it was doing the same thing last fall before we stored it for the winter. I checked the compression and all three are even-135. It will not run on any one cylinder, but will run on two. When I do get it going it still smokes a fair bit, with smoke and heavy fuel mixture coming from the PTO carb.

    Any ideas on what to try next. The machine was rebuilt in 1995, a new starter last year and had the carbs cleaned at that time, it ran great all summer except for the bogging late last season...
    Stuff is coming up out of the PTO carburetor? That sounds like broken reeds.

    If the reeds are good, I would suggest checking whether the flywheel has twisted out of time. A sheared flywheel key could cause the engine to run badly.

  7. #7
    carb and reeds are of, crank is 3 degrees out. but still only running properly on the front cylinder. Are there seals between the cylinders? The mechanic thinks it must be something mechanic. It this require a tear down of the motor. I have to pay shop rates, so I am running if this machine is worth it.

  8. #8
    BlueFishCrisis's Avatar
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    Quote Originally Posted by ekmols View Post
    carb and reeds are of, crank is 3 degrees out. but still only running properly on the front cylinder. Are there seals between the cylinders? The mechanic thinks it must be something mechanic. It this require a tear down of the motor. I have to pay shop rates, so I am running if this machine is worth it.
    There aren't any gaskets or seals between the cylinders, with the exception of the bearings that the crank rides in. These are metal to metal contact, so could leak between cylinders.....

  9. #9
    Polarisitis loonatik's Avatar
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    Crank shaft service limit is 2 degrees.
    There's no seal between cylinders, they're separated by design. Each cylinder is an engine by itself.
    To pay a shop or do your own work is choice you'll have to make. Most of us just look up info in this forum and do our own.

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