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  1. #1

    Question Also Experiencing High REVVING

    Hello. I am brand new to this forum and am glad to have found it. Through searches I found this thread that is similar to a problem I'm trying to resolve.

    Background:
    I'm Brand new to owning/maintainign ski's...but have done a lot of riding with my brother on his ski's in FL. I'm fairly confident with my mechanical inclination, but have little to no experience working on ski's. An in-law in the Northeast recently bestowed upon me (as half-owner, and to try and fix) a couple of Polaris '93 SLT 750's. They sat for about 2 years with only a few dry starts throughout. One has a battery drain problem (think it's a bad CDI) and the other has a revving problem. The issue I'm looking for assistance with at this point is the revving problem. Ski's haven't been in the water sinece I've had them.

    The Revving problem:
    My issue seems a little different from the one described earlier in this thread, in that immediately upon cold-starting the ski, the engine revs to what feels like WOT, without ever touching the throttle. I shut it down after about 1 second, not wanting to damage the engine. (or smog my entire neighborhood out!) I then checked for any obvious throttle cable/linkage issues and there were none. Throttle returns fully to the stop plate. I tried adjusting idle position to see if it made any difference at all, but it didn't.

    I took off the intake cover (both halves) so I could clearly see what the carbs were doing. (...cable, linkage, choke plates, throttle plates, etc.) All appeared normal, or at least what I'd expect to be normal. I started it again...same symptom, and for the brief moment it was running I tried "flooring" the thumb throttle to see if RPM's would change/go higher but it just opened up the throats of the carbs, making a "throatier" intake sound, but no change in RPM's. I shut down again quickly.

    I guess my main question after reading the posts in this thread, is:

    Do folks here feel my trouble is relevant to this thread as far as suspicion of root-cause? (air leaks or gummed carbs?) Or something else?

    If Air Leak suspected:
    I know it's difficult to say without knowing the running history of this particular machine, but what's the most likely locaton for the leak given a common track record for these machines? (head? intake manifold?)

    If carb/gum issue suspected:
    Are there any recommendations for trying to get them cleaner short of tried and true full disassemblement? I'd like to see what makes ANY kind of difference for improvement of this problem before taking the shotgun approach and just taking everything apart, cleaning and replacing gaskets. (Perhaps get it into the water, anchor it to shore, and try running with carb/choke cleaner?)

    The in-law is mechanically DEclined, is happier than a pig in $hit to let me spend all my time on these machines, then split the cost for parts. Time is also a factor as my job consumes 6 days a week, so getting to the heart of the problem quickly and efficiently is the goal.

    Sorry this post is so long. Any advice or re-direction to other threads on the issue is surely appreciated. TIA, looking forward to more participation in this forum.

    Brian


  2. #2
    Watcon's Avatar
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    Air leaks

    I would reccommend a leak-down test for both skis. It often happens when watercraft sit unused for the winter, the crank seals or gaskets will harden up and cause a potential leak...

    If you feel lucky, you can drop it into the water, start it up and take it for a ride and the warm tempeerature might soften up the crank seal again?? You can also remove the flywheel cover and look for oil / gasoline etc, as this will show up if the Mag crank seal is leaking.

    Most air leaks are around the carburetor inlet and base gasket areas.If one carb isn't getting enough fuel, it can cause a small "run-away" condition.

    You should either purchase a leak test kit or make your own.. http://www.watcon.com/Catalog_Pages/...n_Test_Kit.htm

    Regards,
    Randy

  3. #3
    Moderator beerdart's Avatar
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    Brian Welcome to the Hulk.
    I moved your post to its own thread as the 785's are way different.
    Its nice to see another CT Polaris owner..
    You can try the water thing but I think its a waste of time. I would try the leak down test first as Randy mentioned. Lets us know the results.

  4. #4

    Thanks for the reply, Watcon

    What does the leak-down tester test for exactly? And, would I be pressurizing the fuel intake line or something else?

    Thanks.

    Brian

  5. #5
    SeaLion's Avatar
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    A leak down test kit will test your engine for an air leak. It is not done through a fuel line though. Check the kit out at the http://www.watcon.com/Catalog_Pages/...n_Test_Kit.htm link that Watcon posted.

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    It tests the seal of the crankcase. If you have an air leak, you have a lean running condition which will most certinly cause major engine damage. Seal up carbs/intake manifold if carbs are removed. And seal up thje exhaust pipe air tight. Then put 9 lbs of pressure OR vacuum to the pulse fitting on the block. It should hold for a few minutes, if not you have a leak and need to remedy it ASAP.

  7. #7
    cheatin' piston popper addicted's Avatar
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    before you go that far, check the obvious. Are the vacuum port plugs securely installed on the intake manifold? are the hi and lo speed screws in and set to specs? are the fuel lines tight and not leaking? I know it's a long shot, but always check the obvious first.

  8. #8
    SeaLion's Avatar
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    I agree and the most obvious would be a high idle too but still for it to run away like that, right away at start up, is almost guaranteed to be an air leak.

  9. #9
    cheatin' piston popper addicted's Avatar
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    sorry, I should have clarified. I mean look for obvious sources of an air leak. because it is definately an air leak

  10. #10
    SeaLion's Avatar
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    You mean we can't read each others minds after all these years?

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