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  1. #1
    RA_Crash's Avatar
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    94 SL 750 Stalls going from Idle to WOT

    I am new to here and am hoping one of you guys can give me a little help and suggestions. I purchased a couple of jet skis late last year. One of them happens to be a 94 SL 750.

    I was told all it needed was a fuel pump. Over the winter I decided if it needed a fuel pump I should check compression and rebuild the carbs. Did a compression test and found that the MAG was 110 and the CEN and PTO were 120, according to everything i have read that should be ok.

    Tried to take the carbs off and found myself rounding one of the nuts and decided to pull the motor. Now this is my first 2 stroke toy (well toy that does not have 4 wheels and a steering wheel).

    Reading up on this forum I have found out and learned quite a bit. I ended up getting in touch with Ziggler and he was a big help. I took my carbs and engine down to him to learn a few things and it turns out the engine was shot.

    Zig ended up selling me a short block (low hours and passed a leak down test) and had him rebuild my carbs right away.

    Did all the things suggested in these great posts. Here is the list of everything done.

    -New Short Block
    -Rebuilt carbs
    -replaced all the fuel lines (in the tank as well)
    -oil pump delete with cap from Zig
    -new fuel filter
    -new gaskets for everything needed
    -Triple output fuel pump upgrade

    So here is where the fun begins........I took it out on the water and going from idle to WOT it stalls and wants to die. If i hold the WOT it will die. I have played with the low speed carb setting and that seems to have no effect. I have spent a lot of time reading and researching things on this forum but nothing seems to match my issues. If you hold the choke it does help a little bit but still really weak on acceleration. When you do get it going the SL will only rev to 4100 RPM under load (no it is not the limp mode, it revs just fine with no load)

    I am looking for help or suggestions on where to go from here. This is where i am at.

    Compression
    PTO= 125
    CEN= 125
    MAG= 125

    Fuel Pressure 1-2PSI idle
    Home made fuel restrictor = #60 Mukuni Jet

    Idles in the water at 900 RPM
    Spark is present on all cylinders.
    Place timing marks on the new(used) short block in the same spot the old one was.
    Crank index shows to be fine using the "redneck" method mentioned in previous threads

    Also did the cylinder test for poor or bead cylinders and the CEN would not run unless you sprayed carb cleaner directly into the carb. (did not do this much in fear of burning out the pistion rings.) I just did this test tonight and have been struggling with this issue for a couple of weeks now. I am thinking this might be a place to start but cant figure out why the others are working just fine after everything was rebuilt together.

    Would a weak cylinder make the SL 750 want to die under load when going to WOT?
    Could it be something as simple as a clogged jet even though all the carbs have been rebuilt by someone who knows what they are doing?
    Is my next step really to pull the carbs off again and look into why the center cylinder is not getting fuel (i assume it is not getting fuel because the CEN will run with carb cleaner but not on its own)
    If the carb checks out should i do a leak down test again with the intake and exhaust mainfolds still on?

    Are there any things inside these carbs that would make the other 2 work just fine and the one not give any fuel? Again i apologize for some of the obvious questions but just looking for some reassurance that i am heading down the right path.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Welcome

    How can we help?

  3. #3
    RA_Crash's Avatar
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    I just finished editing my first post, i must have posted it before finishing it somehow. Take a look and let me know what you think. Any thoughts or suggestions would be apprecciated.

  4. #4
    RA_Crash's Avatar
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    Here is another question for anyone interested. With these type of 2 stoke watercraft is each cylinder completely seperate from one another in the crank case. I mean do all three buckets share the same fuel/air mixture in the crank case? I would assume that the reason for the triple carbs is to provide the majority of fuel to there respective cylinder.

  5. #5
    BlueFishCrisis's Avatar
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    Quote Originally Posted by RA_Crash View Post
    Here is another question for anyone interested. With these type of 2 stoke watercraft is each cylinder completely seperate from one another in the crank case. I mean do all three buckets share the same fuel/air mixture in the crank case? I would assume that the reason for the triple carbs is to provide the majority of fuel to there respective cylinder.
    they do not share. There are each treated independently. It is possible to have two cylinders running very rich with one running dangerously lean....

  6. #6
    RA_Crash's Avatar
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    Ok thank you....Any thoughts or opinions on post #1. Is my next logical step pulling the carbs again and looking for an obstruction? I assume this carb is not getting enough gas to the cylinder at all, not even enough to fire. Both on the low and the high speed.

  7. #7
    BlueFishCrisis's Avatar
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    Quote Originally Posted by RA_Crash View Post
    Ok thank you....Any thoughts or opinions on post #1. Is my next logical step pulling the carbs again and looking for an obstruction? I assume this carb is not getting enough gas to the cylinder at all, not even enough to fire. Both on the low and the high speed.
    Honestly, I would Call John Zigler Back or pay him a visit. He is a pretty stand up guy and I am sure would help figure out what the problem is, especially since he sold you the motor and serviced the carbs.....

  8. #8
    ripcuda's Avatar
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    Yes, the cases separate each cylinder from one another. The fuel, air and oil sucked in on the piston upstroke then get trapped by the closed reeds on the piston downstroke and forced up through the intake opening into the cylinder. See this ebay listing of split cases for pictures: ebay listing for Polaris 750 cases

    As for your running troubles... how do you have the triple outlet pump hooked up? How do you have the return fuel lines hooked up?

    Cheers!

  9. #9
    BlueFishCrisis's Avatar
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    Quote Originally Posted by RA_Crash View Post
    Ok thank you....Any thoughts or opinions on post #1. Is my next logical step pulling the carbs again and looking for an obstruction? I assume this carb is not getting enough gas to the cylinder at all, not even enough to fire. Both on the low and the high speed.
    You could also check you needle setting on the carbs and verify where they are at vs. factory. I assume John would have set them to factory, but you don't clarify who did final assembly / testing of the whole setup....

  10. #10
    RA_Crash's Avatar
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    John is a Stand up guy, but he is so busy right now, he just does not have the time to really dive into it with me. I can't blame him, I understand what its like being busy. Work is crazy right now for me too. I am looking for help here to relieve him of the pressure. (He is looking at 4 weeks out on service right now, and my patience is not the greatest) With that said, my experience with John has been nothing but great, it is just tough asking him for help when he is pulled in every direction.

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