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Thread: pulse line test

  1. #1

    pulse line test

    My 93' SL750 recently burned a hole in the forward piston. It has the Mikuni 3 outlet pump installed and no kinks/leaks in the lines. What should the vacuum be on the pulse line? What pressure should the fuel pump deliver?
    Many thanks.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Pulse line has alternating pulses of vacuum and pressure, not just vacuum.

    Fuel pressure is 1-2PSI at idle, about 4 PSI at full throttle in the water.

    Make sure you haven't lost the small brass fuel flow restrictor from the return fuel line. If it is missing you will have low fuel pressure at the carbs.

  3. #3
    Connecticut CrazyA's Avatar
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    Check the fuel petcock as well. (on/off/res. switch)

    The 93's were notorious for failing. Little rubber bushing swells and/or rotates and shrinks the opening down to almost nothing.

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  5. #5
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by K447 View Post
    Welcome

    Pulse line has alternating pulses of vacuum and pressure, not just vacuum.

    Fuel pressure is 1-2PSI at idle, about 4 PSI at full throttle in the water.

    Make sure you haven't lost the small brass fuel flow restrictor from the return fuel line. If it is missing you will have low fuel pressure at the carbs.
    Quote Originally Posted by CrazyA View Post
    Check the fuel petcock as well. (on/off/res. switch)

    The 93's were notorious for failing. Little rubber bushing swells and/or rotates and shrinks the opening down to almost nothing.
    Welcome to the Hulk.

    2 great responses there. ^^^^

  6. #6
    Is it better to eliminate the on/off/reserve petcock all together? I did pull the jug and piston today. I noticed water sitting in the crankcase. Did this happen when I pulled the jug or do you think it was there and that is why the pulse was weak and led to my piston burn? I'm fairly certain the piston is stock, where is the best place to get one?
    Again many thanks.

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Keep the petcock. Just replace it with a new Sea doo one.

    How much water? Some will come out when you remove the cyl and head.

    Was there any water inside the pulse hose?

    Fluid inside the pulse hose will weaken the signal to the pump resulting in lower fuel pressure.

    You can get pistons from many places if you use the WSM piston kit. John Zigler, Sharp's marine, Ebay......

  8. #8
    I have decided to remove the engine and give it a top end job. I have cleaned the mating surfaces for the new gaskets. Some debri did get down to the crank cavity and I did my best to blow it out. I then turned it upside down, sprayed with cleaner, and then lubricated the bottom end with 2-cycle oil. Can I leave this oil in there or will it cause problems when trying to start later? Is this the same cavity as where the pulse line originates? If I blow through the pulse line will I be blowing oil out?

  9. #9
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Remove all the excess oil. (leaving a nice coat on the parts is fine)

    Yes that's the same cavity the pulse hose is connected to.

    If you blow air through the fitting, you'll have a mess.

    Better to try and vac the oil out of the case using a small hose. Slipping it between the crank webs.

  10. #10
    Watcon's Avatar
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    Replace the pulse line with higher quality.. NOT the low priced E-bay, etc stuff.. If it has color in it, it's usually too soft!

    Thanks,
    Randy

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