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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
    ph2ocraft's Avatar
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    If it had a leak or hole it would weep out of the atmospheric hole on the diaghram cover.

  3. #3
    1996SLTX's Avatar
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    Quote Originally Posted by ph2ocraft View Post
    If it had a leak or hole it would weep out of the atmospheric hole on the diaghram cover.
    So I should smell the raw fuel in the hull or when I remove the cover to the pump, I'll see raw fuel or both?

    I'm guessing then that before I take the pump apart, I should run the engine to get fresh fuel through the leak if it has one? After sitting for a week or two, would that leaking fuel dissipate?

    Thanks, Ron

  4. #4
    1996SLTX's Avatar
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    I found this online last night....

    Building your own Pop-Off Tester





    This is very simple to make. You can get the pumper bulb at any medical supply store. It is used for doing blood pressure test. It cost me about $6.00. The 1/4" tee and hose barbs I got from N.A.P.A. in the brake fittings section. I have about $3.00 in all the fittings. I got the 0-30psi gauge from Grainger for $2.00. The 1/4" flexible tubing is some old fuel line I had laying around. As you can see this is a cheap alternitive to paying $30.00 to $50.00. Any questions e-mail me below.

  5. #5
    john zigler's Avatar
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    good deal ron. nice tester.

    please remember, it is not always a "leak" that causes problems. diaphragms gan get distorted, and streched over time, and not work properly.

    zig

  6. #6
    1996SLTX's Avatar
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    Thanks John...The ski in question is a 96 SeaPoo XP...won't idle and has to be started at WOT, other than that, runs well and spark plugs are perfect color. It runs well from just above idle to WOT. I'm trying to eliminate a leaking diaphragm as the possible source of trouble.

    The previous owner is a good rebuilder and friend of mine and couldn't figure it out. But he also hadn't checked the fuel pump so maybe I'll get lucky and that will be it.

    Mikuni Super BN 38mm dual carbs

    Any ideas? Thanks!

    Quote Originally Posted by john zigler View Post
    good deal ron. nice tester.

    please remember, it is not always a "leak" that causes problems. diaphragms gan get distorted, and streched over time, and not work properly.

    zig

  7. #7
    john zigler's Avatar
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    we rebuild ALOT of carbs here, and i can easily say, 95% are seadoo's.

    the 96 XP 787 has SBN "I" series 40's on it. seadoo's of that era are known for the poor quality fuel lines. they go bad, from the inside, and gum up the carbs.

    i would stongly suggest going through the carbs completely. make sure they are ultra clean inside, replace all gaskets, diaphrams, valves, ect. also replace the needle and seat. use only GENUINE mikuni brand parts. you can find kits, and parts real cheap, but you do get what you pay for, and will end up doing the job over again.

    i am going to bet that iff you pull them apart, you are going to find a mostly blocked internal fuel filter, and a "wear ring" on the tip of the needle & seat.

    i will also bet, when oyu pull them off, and if you look into the fuel lines, you will see "gunk".

    you should also replace all the grey tempo fuel lines. you can use std 1/4 automotive fuel line from napa, auto zone, ect.

    good luck. zig

  8. #8
    ph2ocraft's Avatar
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    Sounds pretty much like a Polaris issue with the fuel system.........but no lost cylinder, cool to know zig.

  9. #9
    1996SLTX's Avatar
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    Just found out the carbs haven't been rebuilt during the time my friend had the ski and he bought the carbs to replace some aftermarket mods he didn't like that were on the ski when he got it, so that will be on my list of things to do....so we're thinking that there's a fuel leak in the low speed circuit?

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