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Thread: 98' 40hp Yamaha

  1. #1
    Join Date
    Feb 2008
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    Upstate
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    3,926

    Default 98' 40hp Yamaha

    Ran for first time in 4-5 months.

    Give it fresh gas, ran the internal tank dry after last use.

    Started fine. After 1/2 throttle, it started to "bog" down. Ran fine at 1/2 throttle, but would try to flood if you gave it any more.

    Spark plugs, then carbs?

  2. #2
    Join Date
    Dec 2011
    Location
    Rock Hill SC
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    9,154

    Default

    Carbs.

  3. #3
    Join Date
    Aug 2009
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    PeeDee
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    Default

    Give it some seafoam.

  4. #4
    Join Date
    Dec 2009
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    Hampton Co./Bluffton
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    7,817

    Default

    Carbs
    Quote Originally Posted by Chessbay View Post
    Literally translated to, "I smell like Scotch and Kodiak".
    "Let us cross over the river, and rest under the shade of the trees"- Gen. Thomas "Stonewall" Jackson

  5. #5
    Join Date
    Feb 2008
    Location
    Upstate
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    Default

    Is it common for the carbs to gum up after it sits a long time? It was running normal on the last use. I thought plugs were more likely, was dark so I didn't even pop the lid.
    Last edited by Murray; 11-20-2013 at 12:02 AM.

  6. #6
    Join Date
    Jul 2006
    Location
    Springfield, Ga
    Posts
    360

    Default

    This is what you need

    2 Cans of Berryman B-12

    1 Gallon Gas can

    Fill gas can add B-12(add oil if not pre mix)

    1. Drain the carbs via the screw at the bottom of the bowl. Mostly likely the gas will be brownish when it comes out. Replace screw.

    2. Run motor on the gas can and Chem B-12 until motor stops missing.

    3. Repeat with second round of Gas and B-12 if needed.(My yamaha took two rounds)

    I added new reeds shortly after doing this and broke down the carbs just to see the results of the flush. They was only a small about of trash in the very bottom of the bowls and it had to be scraped off with a screw driver to remove.

    If this does not work, order some yamaha carb cleaner and soak them in it. That cleaner is some damn good stuff.

  7. #7
    Join Date
    Oct 2007
    Location
    Blythewood
    Posts
    16,975

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    "Freedom Isn't Free"
    _Spc. Thomas Caughman
    1983-2004

    Quote Originally Posted by Dook View Post
    Go tigers!

  8. #8
    Join Date
    Mar 2002
    Location
    greenville
    Posts
    1,550

    Default

    Sea Foam did wonders for me.

  9. #9
    Join Date
    Nov 2013
    Location
    God's Country
    Posts
    8

    Default

    Only way to fully solve the problem. Disassemble carbs, soak, put back together, drive it like normal.

  10. #10
    Join Date
    Jul 2004
    Posts
    3,642

    Default

    Quote Originally Posted by treeshaker View Post
    Only way to fully solve the problem. Disassemble carbs, soak, put back together, drive it like normal.
    x2

  11. #11
    Join Date
    Jun 2011
    Posts
    3,676

    Default

    Blown top cylinder. ..I'll give ya 50 buck right now
    "Think A Guy Like Me Worries About Percentages?" Tin Cup

    "Some get spiritual cause they see the light, and some cause they feel the heat" Ray Wylie Hubbard

    "P.S. I love turkeys. Mostly just hate those who hunt em." Glenn

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