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  1. #1

    '93 SL 750 Update

    I posted a while back about a "free" Polaris I got my hands on.

    I did replace a head gasket that was obviously blown. Along with the blown gasket, one of the studs was stripped. Go figure. It took a couple of attempts, finally requiring a helicoil insert, copper gasket sealant, and good bit of lapping done to the sealing surface.

    New battery, too.

    The engine seems to function properly now: What it get going, it runs hard and fast. The running temp seems reasonable. No leaks, no noises. Good, strong sound.

    The problem now seems to be tune-up. To get the ski running fast, the driver must pull slightly on the choke and wait. For a long time, possibly. Once all three cylinders kick in, the ski will remain fast. Come off the and you have to do the same thing. It has two speeds, idle and WOT. No throtttle control in the middle.

    Any recommendations for carb tune-up? Again, the engine seeems to run mechanically sound, if and when it gets going.


  2. #2
    bowsniper's Avatar
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    Still thinking

  3. #3
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    Needing to choke her to get her to go is indicative of a lean condition. Continuing to run it like that will cause engine damage. You need to rebuild/clean the carbs. If the fuel lines are original (grey Tempo brand), they need to be changed out. All of the lines, including the ones in the fuel tank, and change the filters. You might even want to upgrade the fuel pump to a triple outlet pump, although someone highly regarded around here recently said a single will do the job.

    To keep the oil injection system reliable, change the oil filter, and lines too.

  4. #4
    johnsonmtz's Avatar
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    Quote Originally Posted by jocko_nc View Post
    The problem now seems to be tune-up. To get the ski running fast, the driver must pull slightly on the choke and wait. For a long time, possibly. Once all three cylinders kick in, the ski will remain fast. Come off the and you have to do the same thing. It has two speeds, idle and WOT. No throtttle control in the middle.

    Any recommendations for carb tune-up?
    The engine is running lean. A hesitation that requires the chokes to richen the mixtures means there is not enough fuel getting to the engine.

    Here's the list of must do's to get the fuel system in shape:
    1) Disassemble the carbs. Clean all orifices and filters, replace all gaskets, diaphragms, o-rings, and flapper valves with new ones from genuine Mikuni kits.

    2) Install 3-outlet pump and re-plumb carbs for the new pump

    3) Check and clean fuel shutoff valve.

    4) Replace Fuel lines.

    5) Check pop-off pressure of carbs once they are rebuilt.

    If you do all this, the ski will quite possibly run just fine.

    KJ

  5. #5
    That's about what I was figuring... Looks like a fall project. This thing ain't safe to operate with boat traffic.

    I'll throw this out as a hail-Mary: The ski no doubt had a "failing" gasket for some time. The pitting and erosion on the aluminum shows that. It had to be running funny for a while. The prior owner would show up on Friday afternoon and want to ride. He would take it to the local marina-and-bait-shop "mechanic" guy to get it running. (Hence, stripped stud, etc.) What are the odds he fiddled with the carburator on that cylinder to make it run, albeit incorrectly? What adjustment would he have made? A mixture adjust? Is that orifice fixed? Let's say the ski "ran" like that for a while, but ultimately lost compression. Now, the cylinder is back in order, but the carb is too lean. ??????.

    Thing is: The same mechanic told the owner that parts are obsolete and unavailable for this ski. I know nothing of these things, but quickly found that not to be true. The blown gasket was a no-brainer even for a novice. The upper cylinder is about as complicated as a Lawn Boy. The lower end, now that is a bit more complicated. I'm eye-balling that one cylinder.

    Oh yea... Carburators scare me. The ultimate project where you end up with "extra" parts left over.

  6. #6
    It's a JEEP thing...You wouldn't Understand dirtdude35's Avatar
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    Quote Originally Posted by starflight View Post
    Needing to choke her to get her to go is indicative of a lean condition. Continuing to run it like that will cause engine damage. You need to rebuild/clean the carbs. If the fuel lines are original (grey Tempo brand), they need to be changed out. All of the lines, including the ones in the fuel tank, and change the filters. You might even want to upgrade the fuel pump to a triple outlet pump, although someone highly regarded around here recently said a single will do the job.

    To keep the oil injection system reliable, change the oil filter, and lines too.
    +1. my friend just blew two pistons in his 94 750 because it was lean.

  7. #7
    I found the carb manual...

    As I read it:

    The Idle is a screw-stop.
    The Low Speed is a screw adjust.
    The Pop Off is a fixed spring rate.
    The High Speed is a screw adjust.

    I don't think the problem is the Idle or Low Speed. No way anyone messed with the Pop Off. I'm thinking High Speed adjust.

    Would someone mess with the High Speed adjust, perhaps lean it out, to compensate for a compression loss? Would that theoretically work for the shadetree "mechanic"?

  8. #8
    Bing-A-Ding-Ding-Ding, Brrrrrap! Brrrrrrrrrap!!! Polaris_Nut#1's Avatar
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    I don't have the specs for a 93 but turn them in till they seat and back out to factory spec. They will all be different. Count as you turn them in and you can compare to factory specs and you will know if one was messed with.

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