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  1. #1

    98 Gp760 questions (oil smoke/runoff & impeller)

    Hello all. New to this forum, and I have to say, WOW. It is great. There is a ton of knowledge here, and I have learned more here in a few days than in the past 5 years of owning my ski.

    Anyways, 2 problems with my ski that I need to figure out what to do.

    #1. I am having some serious oil burn issues on the ski. I don't premix, and don't want to due to the amount of people that use the ski and that I don't trust w/ premixing. But the problem is that it smokes way too much. I just smoked out the neighborhood trying to trouble shoot what it could be. When I put my hands under the exhaust water (running on shore w/ coolant water hooked up) the water is beaded with tons of oil. It seems to be getting worse.

    The manual doesn't tell me how to adjust the oil flow from the oil pump. so I don't know what to do. I don't have a compression tester, so I don't know if it's burning the full gas/oil/air solution properly.

    Any suggestions on what this might be, or where I should start looking. I am ok w/ engine basics, but if this is a seal or something of the likes, I don't want to tear into it by myself..though the rate of $80 an hour at our local shop is a bit high for me.

    #2. I have a serious porpoise issue that is new. Not the old GP760 standard, where at high speeds you have issues. This is new, at 20mph it is unridable. I am wondering if a worn out impeller could be the issue, cavitation causing serious thrust issues? Ride plate is striaght, hull is intact and ok. Engine mounts are good. Thoughts?


    Any help is greatly appreciated.

    FlynHokie


  2. #2
    One more thing...sorry

    If I do have to replace the impeller, what one would you recommend, while trying to stay on the inexpensive side?

    When you do replace it, where to you place sealant w/ the intake grate? I don't see that mentioned in the service manuals.

  3. #3
    cheatin' piston popper addicted's Avatar
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    Welcome.

    First, if you didn't download the manual, do so. It's in the Yamaha how to section.

    Next, I don't know if that ski has a variable oil pump, but if it does the adjustment procedure is in the service manual. You can tell if there is a cable going to the oil pump or not. If not, all you can really do is switch to a good synthetic oil, such as amsoil. Synthetic oil burns cleaner, so there is less smoke. Pricing is very competitive, especially if you sign up as a preferred customer. Check it out here https://www.amsoil.com/amsoillogin/p...spx?zo=1520362
    and here http://www.amsoil.com/storefront/hpi.aspx?zo=1520362


    If your carbs have never been apart, it is time to concider a full rebuild. Leaking internal parts can cause running issues, or worse, plugged internal parts can cause engine failure.

    Try a longer ride plate to control the porpoise. The prop really can't make it porpoise. look for a solas or skat track prop on eBay. They can be found pretty cheap. Not sure witch one for that ski, so hopefully someone else can help you with that.

    Lastly, try posting in the old school section. It's dedicated to pre GPR ski's.

  4. #4
    Did download manual, and there is no way to adjust the oil pump.

    Thanks for the input. Will cross post this in the oldschool section too.

    Time to search on how to rebuild carbs

    Edit: Didn't find much on rebulding a carb. I've never done one before. Is there anything I should worry about, be warned about? I've got the service manual, and it shows the parts. I'm assuming I just take apart and clean it. replace worn parts if necessary?
    Last edited by FlynHokie; 08-28-2007 at 07:26 PM.

  5. #5
    cheatin' piston popper addicted's Avatar
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    pretty simple. Just buy the mikuni kits. replace the seals and diaphrams, and most importantly, replace the needle & seat and the internal filter.

    Do 1 at a time so that you can use the other for reference. The mikuni manual is posted everywhere. Look for that and download it too. YOu should be able to find it in the polaris tech scetion.

  6. #6
    Ok, just took the first carb apart and cleaned it. It appeared to be very clean for not being done in 9 years....

    What Mikuni kit do I need? Should I take apart the fuel pump section also?

    I've looked for the Mikuni manual (on their website), but I'm not sure exactly which carb it is? Any idea? The manual doesn't say.

    Also, are the 2 gaskets that go between the engine & the carb and the carb & the upper carb assembly (surrounding both carbs) come with the kit. The top gasket was messed up on my ski, and might as well replace the bottome one while I'm at it.
    Last edited by FlynHokie; 08-29-2007 at 06:13 PM.

  7. #7
    Well, I rebuilt the carbs on the 98 gp760. It wasn't too difficult.

    I put them back on the ski tonight, and started it up, and it was still smoking. Not sure if it was burning off residual oil or if it was still spitting out oil like before, since it was dark outside by the time I could start it up.

    I'll restart it tomorrow am, and let y'all know what I come across.

  8. #8
    Moderator OsideBill's Avatar
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    Quote Originally Posted by FlynHokie View Post
    Ok, just took the first carb apart and cleaned it. It appeared to be very clean for not being done in 9 years....

    What Mikuni kit do I need? Should I take apart the fuel pump section also?

    I've looked for the Mikuni manual (on their website), but I'm not sure exactly which carb it is? Any idea? The manual doesn't say.

    Also, are the 2 gaskets that go between the engine & the carb and the carb & the upper carb assembly (surrounding both carbs) come with the kit. The top gasket was messed up on my ski, and might as well replace the bottome one while I'm at it.
    You can get a copy here in the "how to section" under "Yamaha service manuals"

  9. #9
    Quote Originally Posted by osidebill View Post
    You can get a copy here in the "how to section" under "Yamaha service manuals"

    Yeah, service manual already downloaded. For some reason, I had issues with the fuel pump on the first carb. It is done though.

  10. #10
    Moderator OsideBill's Avatar
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    Did you get both the GP and the Mikuni manuals?

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