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Thread: Yamaha 30 3 Cyl - Why Is Oil Present And Dripping From....

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    Default Yamaha 30 3 Cyl - Why Is Oil Present And Dripping From....

    My bottom 2 carbs have oil residue that builds up and is visible on the intake side of the bottom 2 carbs but not the top carb. The oil drips down to the lower cowl and finds its way to the clamp on bracket and eventually to my driveway.

    Motor has boyesen reeds and i lapped the reed cages with super fine wet dry sand paper until the reeds made a good seal and i say that because i received a suggestion to check the reeds.

    Any other ideas that could cause this? Same issue is present on another yamaha as well.

    Thanks fellers

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    My best guess is it just gas/oil mix that manages to seep out from the carbs after it's left sitting. The gas evaporates as it manages to seep out from carb bowls leaving the oil to drip. I've seen plenty have some oil residue or small drip off the bottom carb or two. Enough to drip on the drive way seems a little excessive. Are you storing it with the engine tilted up? This is my best guess, not a for sure diagnoses could possibly need bowl gaskets on the carbs or something else that is allowing the gas/oil to seep out from the fuel system.

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    My old yamaha 30hp had a misty vapor coming out of the carb bores at high speeds until I installed Chris Carson race reeds with reed blocks from the yamaha 40/50 hp.

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    Dumb question: Do you run the fuel system dry after a run? That can cause dripping and make a mess in the carbs.

    Like I said, a dumb question!

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

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    My yamaha 30 3 cylinder does the same thing. Oil all over the clamp on bracket. Gotta wipe ot down a few times a year.

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    I too lapped my reed cages (mine has 40 hp cages) with a fine wet dry sandpaper. I later was told to use a course grit as it would leave more surface area for oil to cling to. Have not made that change though.

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    Don't know about Yamis Pyramid style reed cages but the old doughnut Merc reed cages (55H, 44xs, etc) are prepped with pretty course paper in a 90 degree cross pattern (used by Jerry Wienandt racer & engine builder, ret.). I do my Merc 25ss doughnut cage per Jerry's method.
    No man's life, liberty or property are safe while the legislature is in session.

    Location: SW Orlando, Fl

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