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  1. #1
    1996SLTX's Avatar
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    Mikuni SBN Fuel Diaphragm Test...

    I don't have a tester...is there another way to test the fuel pump diaphragm for leaks or holes?


  2. #2
    96XPSS's Avatar
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    They normally leak fuel when there is a rupture. There is a vent hole on the cover plate, and gas will pour out of this.

  3. #3
    IF you dont have fuel in it ,or carbs on bench,or it has pin hole,Pull vacuum on pulse inlet of carb ,see if it holds,If carbs on watercraft and you dont have a small vacuum pump with gauge,you can remove pulse line from carb,install a 1' section of hose to pulse inlet,make sure it is good snug fit,then put in your mouth and suck on tube,place tongue over tube end and see if it holds a vacuum.This is a quick way to tell.it doesnt take much of a leak,for vacuum to drop off.Before any of you pros laugh it does work for a quick check to see if pump diaphram has a hole in it,or leak around back side of it.Now if the carb diaphram that actuates the needle ,has a hole in it,there is a weep hole that fuel will flow out of,but this is not on fuel pump side of carb, In my 15yrs. plus of mikunis This is much more a problem area than fuel pump,also mikunis get the small filter behind the fuel pump filled with a little trash,this causes loss of performance ,hard starting,and a lean running conditionJMHO>Marvin
    Last edited by mrjetskey; 11-24-2007 at 10:49 AM.

  4. #4
    1996SLTX's Avatar
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    Quote Originally Posted by mrjetskey View Post
    IF you dont have fuel in it ,or carbs on bench,or it has pin hole,Pull vacuum on pulse inlet of carb ,see if it holds,If carbs on watercraft and you dont have a small vacuum pump with gauge,you can remove pulse line from carb,install a 1' section of hose to pulse inlet,make sure it is good snug fit,then put in your mouth and suck on tube,place tongue over tube end and see if it holds a vacuum.This is a quick way to tell.it doesnt take much of a leak,for vacuum to drop off.Before any of you pros laugh it does work for a quick check to see if pump diaphram has a hole in it,or leak around back side of it.JMHO>Marvin
    Sounds great....and the taste of fuel is one of my favorite flavors! I'll give it a try....thanks everyone...great advice keeps these skis affordable and fun!

  5. #5
    You wont taste fuel if it doesnt leak!!! Unless you know it is fuel pump,I would be looking at the filter first,then the diaphram on other side of carb opposite the intake -outlet-vacuum lines.I do mean the small fuel filter inside of each carb. not the big one before the carbs,hope this helps>Marvin
    Last edited by mrjetskey; 11-24-2007 at 10:54 AM.

  6. #6
    1996SLTX's Avatar
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    Hope for the best, BUT plan for the worst!!

    Actually, I'm hoping for a leak....that would be great....mysterious issues drive me nuts...

  7. #7
    1996SLTX's Avatar
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    Quote Originally Posted by mrjetskey View Post
    You wont taste fuel if it doesnt leak!!! Unless you know it is fuel pump,I would be looking at the filter first,then the diaphram on other side of carb opposite the intake -outlet-vacuum lines.I do mean the small fuel filter inside of each carb. not the big one before the carbs,hope this helps>Marvin
    Wouldn't clogged internal filters kill my top end? From just above idle to WOT, the motor sings...and the spark plugs look perfect.

  8. #8
    96XPSS's Avatar
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    Quote Originally Posted by 1996SLTX View Post
    Wouldn't clogged internal filters kill my top end? From just above idle to WOT, the motor sings...and the spark plugs look perfect.
    Yes, you are absolutely correct.

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