SBT Jetski Engines, Parts & Accessories

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  1. #1
    Joined
    May 2005
    From
    Highland, Michigan
    Posts
    73

    Default help with 720 engine starting problem

    Hey folks,
    I have a problem with my seadoo 720. When its cold it seems to start right up and after riding it for a while it becomes difficult to restart. have to hold throttle wide open for it to start. Once it starts it has no throttle responce (idles but does not respond to throttle). about 10 seconds later it picks up and runs fine.
    I have rebuilt both carbs and fuel pump and and have adjusted to SBT recomended setting. I did try turning the low speed needle in an 1/8 of a turn. This did not seem to help. Fuel filters are clean. Fuel selector is clean. Seems to be a rich condition but plug check looks coco brown after low speed check.
    Anyone have any ideas.
    Thank you
    Schultztec

  2. #2
    Joined
    May 2005
    From
    Highland, Michigan
    Posts
    73

    Default Re: help with 720 engine starting problem

    BTW, I used the stock springs for popoffs.

    thx
    Schultztec

  3. #3
    Joined
    Jul 2004
    From
    Ft Worth Tx
    Posts
    1,095

    Default Re: help with 720 engine starting problem

    When you did the popoff test dd you do a leak down test for the needle and seat valve and did you replace those (needle and seat) when you did rebuild?

  4. #4
    Joined
    May 2005
    From
    Highland, Michigan
    Posts
    73

    Default Re: help with 720 engine starting problem

    yes sir I did replace the needle and seat. used the old spring that was in the carbs before the engine was replaced. However I did not do a leak down test because i do not have a pop off guage. I was hopeing since i used the factory springs pop off would be close ??

    thx
    schultztec

  5. #5
    Joined
    Jul 2004
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    Ft Worth Tx
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    Default Re: help with 720 engine starting problem

    should be close what are your settings as far as hi and low speed screws?

  6. #6
    Joined
    May 2005
    From
    Highland, Michigan
    Posts
    73

    Default Re: help with 720 engine starting problem

    high speed it all the way in or 0 (per sbt chart) and low speed is 1 1/4 from there I leaned the low speed down 1/8 in but did not seem to help. It sure seems like my pop off pressure is to low. I may have to purchase a guage.

    thx
    Schultztec

  7. #7
    Joined
    Jul 2004
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    Ft Worth Tx
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    1,095

    Default Re: help with 720 engine starting problem

    it would be best to do so as I am not sure what you had before it may have had the wrong spring in it and not knowing what it is makes it hard to tell you to do this or that

  8. #8
    Joined
    May 2005
    From
    Highland, Michigan
    Posts
    73

    Default Re: help with 720 engine starting problem

    yeah, i guess i will have to do the test. The carbs were all stock but i wonder if the sprins could have gotten worn out from use. Hence lower pop off pressure ??


    thx for the replys
    schultztec

  9. #9
    Joined
    Jul 2004
    From
    Ft Worth Tx
    Posts
    1,095

    Default Re: help with 720 engine starting problem

    it is possible do you happen to know how old the old spring was or is?

  10. #10
    Joined
    May 2005
    From
    Highland, Michigan
    Posts
    73

    Default Re: help with 720 engine starting problem

    Not 100% sure but i would bet it was original factory 1996

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