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  1. #1

    Why do PWC have Pulse and Return Lines?

    I am new to the world of PWC. Come from a dirt biking background. I understand carbs in a dirt bike but have run into some new things to understand in PWC.

    I have looking in my service manuals but they don't explain the purpose of return lines and pulse lines. Can anyone explain or direct me to tutorials? many thanks.


  2. #2
    Dr Len's Avatar
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    Pulse lines are a vacume to move the diaphram in the fuel pump on the side of your carbs. It keeps constant fuel pressure to your carbs. the pressure get to great. Thats what the return line is for. To route the fuel back to the tank. In a nut shell.

  3. #3
    100 MILES OF HEAVEN AND I AM SMACK IN THE MIDDLE KEYZBUM's Avatar
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    Quote Originally Posted by kdxcookie View Post
    I am new to the world of PWC. Come from a dirt biking background. I understand carbs in a dirt bike but have run into some new things to understand in PWC.

    I have looking in my service manuals but they don't explain the purpose of return lines and pulse lines. Can anyone explain or direct me to tutorials? many thanks.
    the pulse line is the "push pull" action from the crankcase that moves the diaphram in the fuel pump ...
    the return - is just that ,,these carbs are overpressured in fuel so they work at wierd angles and to make it to all(3) carbs..
    thats my 2 cents --others will fill in what i forgot..
    mattman

  4. #4
    check this out http://www.mikuni.com/pdf/sbn_manual.pdf
    basically jet ski carburetors are pressurized and use a pop off for pressure instead of a float needle like a dirt bike... it needs the crankcase pulse line to pump gas into the engine because their is no gravity to feed it... it has to be this way because the engine comprtment is sealed, and there is no where for the fuel to leak to... and also the g forces of the ski in the water will have an effect on the fuel delivery...

  5. #5
    My Jet Ski drinks more than yours Glenozzy's Avatar
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    to check if the heart is beating

  6. #6
    Thank you for the excellent information gentlemen! Now I understand, more or less. Great explanations.

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    The pulse line is connected to the block through a fitting. Everytime the piston moves down, it creates a + pressure (push). Everytime the piston moves up, it creates a - pressure (pull).

    This push/pull movement is transfered to the fuel pump's internal diaphragm via the hose. This happens thousands of times a minute. So every pull, sucks fuel from the fuel tank, and every push, forces it to the carbs.

    As for the return: The ski requires a closed loop fuel system. Meaning, in the event of a flip over, fuel CANNOT empty into the water. So floats and overflow vents are eliminated. Therefore surplus fuel needs to be returned to the tank.

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