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Thread: The old dog dogs

  1. #1
    Member sayak's Avatar
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    Question The old dog dogs

    I have a '96 Polaris 440 Indy Sport Touring of which I have been the sole owner. It is rough in appearance but only has about 1200 miles on it. I have done a lot of ptarmigan and caribou hunting, and ice fishing using this old sled, so I'm kind of sentimental about it.

    For the last several years it has had this problem of dogging when it warms up. By "dogging" I mean that if I back off on the throttle it will try to die. When it is in this mode, I can add choke momentarily and it will move enough for me to get it up to speed again, but will do the same thing if I back off again. After several miles it will eventually die and be rather difficult to get re-started.

    I've had the machine in to the local Polaris dealer, and it was supposedly fixed, but this was at the end of the season spring before last, and it was melting by the time I got it back so I never really tried it out. When I used it last winter, it was the same old story.

    Just yesterday I decided to try to repair the machine on my own. I knew there had been water problems before, so I completely drained the tank, all the way to putting an old towel in it to wick up any moisture. I changed out all the gas line, put in a new in-line filter, rebuilt the fuel pump, and disassembled and reassemled the carbs, looking for any dirt, wear or moisture in the float bowl and main jets. There was none that I could see. I also let the carbs sit in isoproyl alchohol overnight to soak up any residual moisture that might be in any orifices of the carbs. Basically the whole fuel system was overhauled. Put in new plugs too for good measure.

    Sooooo..., I reassembled everything and it pretty much started up and ran well for awhile and then it did the same old thing all over again. I'm pretty discouraged and totally stymied. Any ideas old throttle jockies?

  2. #2
    Member Adventure's Avatar
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    Default

    My old skidoo did that and it turned out to be the crank seal on the mag side sucking air.

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    Member sayak's Avatar
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    Default Hmmm....

    How would that work? How did you figure it out? Did your machine have reed valves?

    I'm thinking it has to be a mixture problem, because when I add choke it will stop dogging for a few seconds. Low speed jetting?

  4. #4

    Default Air

    You are likely sucking air somewhere. Through a seal or a gasket or possible a cracked boot between the carb and the jug. Look at the plugs. One should be looking closer to white and that might tell you which side to start on. I'd take my propane torch and turn in on without lighting it and move it around the likely areas and see if the idle increases - if you can get it to idle. When you turn the choke on you are increase the fuel in the mix and getting it to run....probably really rich on one side and somewhat closer to normal on the lean side.

  5. #5
    Member sayak's Avatar
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    Default Cracked carb flanges

    I thought about those boots. Maybe when they heat up, a crack opens. The rich side would be good side though, wouldn't it? Since when I choke it it runs better? Also, since a crack would be letting in air and thereby leaning out the mixture? You're right, the plugs should tell me the story.... I hope.

    I'll try the propane trick, that sounds like a slick idea.

    The idle doesn't seem to be a problem. It actually idles a little fast.

  6. #6
    Member sayak's Avatar
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    Default No cracks

    Pulled off the flanges for an inspection. No cracks. Resealed them with gasket sealer and tightened them up. Also tightened clamps as far as possible. There were two sets of nipples on each carb w/o any hoses on them (primer?), so sealed them off with pieces of cinched tubing. Gave her a test run and same old thing. Ran out of daylight to really examine plugs. Seems that it isn't an air leak there, however. Any further ideas?

  7. #7
    Member Adventure's Avatar
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    Default

    It still seems like an air leak somewhere. The crank seals and engine gaskets can leak intermittently so can be hard to diagnos. Starving it for fuel if that's what it is will over heat and eventually melt a piston. If you see any shiny aluminum specs on the plugs it is a sign of predetination caused by lean conditions. I ended up yanking the engine, plugging all openings and pressurizing it under water to find the leak.
    No reed valves as this was a seventies skidoo.

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    Default Vacuum gauge

    If you have a vacuum gages, measure the vacuum at the port going to the fuel pump. On my polaris 500 (488) it was 3 to 10 inch of vacuum.

    If you don't have a vacuum gages a peace of paper may works. On my engine the oil seals were ok, and I had good compression but no vacuum. I put in new rings and pistion to fix my problem.

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    Member sayak's Avatar
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    Thumbs up Thanks guys

    I appreciate the responses. I'll try pulling the hose to the crankcase vacuum nipple and use some paper to see what happens. I don't have a guage to do that unfortunately.

    One thing I forgot to mention in my original description of the probem: If I don't turn off the petcock when the machine is not running. it will hydrolock the crankcase. Probably not related, but I thought I'd toss it in.

  10. #10
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    Default Have you every Drain the crankcase?

    Are there two crankcase drains (looked liked a bolt) in front of the engine under the exhaust ports? If so, remove them and see if gas comes out.
    If you have a leaking float in the carb., and leave the petcock on, it could fill your crankcase with gas.

  11. #11

    Default crankcase with gas


    If you have gas leaking into the crankcase itís usually a bad needle seat or fuel pump. Did you check to make sure your floats are working, I've had them get water logged, and they looked fine until I put fuel into the float bowl and noticed they didn't float.
    Itís had to tell whatís wrong without out looking at the machine, have you checked your throttle free play there are two micro switches that are connected to your kill switch they have been known to go bad or stick.


  12. #12
    Member sayak's Avatar
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    Default Hydrolocking

    My friend had the same problem with his Polaris. Seems to be common.
    I checked the floats when I pulled and cleaned the carbs. Both were light and liquid free. Main jets were fine. Float levers looked to be adjusted where they should be. I just replaced the whole fuel pump. I have had experience with that throttle switch, so I checked it out already, but will check again. Maybe it is sticking.

    I am going to check for crank case drains today, as I've never noticed them.

    Again, thanks for your responses. People on this site are a real community. Kinda like being broke down on the trail.

  13. #13

    Default "dogging"

    Could you give a little more detail about dogging, is it only at idle that the problem occurs, how does it run past 1/4 throttle.

  14. #14
    Member sayak's Avatar
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    Default Well...

    I wish I could answer that onstep!

    Yesterday it was running OK at high speed but would bog at low speed unless I teased it with the choke. But today I can't get it to go more than 50 feet without it stopping, even with teasing it with the choke. I don't know what happened overnight. Plugs look OK, though both look like they're running rich. Throttle stop switch is functioning OK, (I think), going in and out easily.

    I drained the crank case and found a little gas in it before I tried to run it today. But after my "trip" of maybe 300 feet- in spurts- to the trailer (to take it to a shop) I drained the crank case again and found more gas. Bad rings?

    Now I cant even get it to start to get it up on my trailer. Didn't check the spark, because I've never suspected the ignition to be a problem.

    I'm about ready to torch the old beast!

  15. #15

    Default carb

    There were two sets of nipples on each carb w/o any hoses on them (primer?), so sealed them off with pieces of cinched tubing.

    Try taking the tubing off and see if it gets you back to where you were.

  16. #16

    Default carb

    Itís hard to tell without looking at it, but you might have sealed your vent tubes off, some models vented in the engine compartment others vented to the air box.

  17. #17
    Member sayak's Avatar
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    Default Which ones?

    Thanks again onstep.

    Would the vents be the nipples closest to the cylinder or the airbox? What do they vent anyway? Guess I could try both. Also, would it be normal to have gas in the crank case or not?

  18. #18

    Default carb

    It provides float chamber venting on some models.

  19. #19

    Default carb

    If you undo the vent lines and it runs fine above 1/4 throttle (like yesterday) you might just need to synchronize your carbs and adjust the pilot air screw.

  20. #20
    Member sayak's Avatar
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    Default Will do

    I'll do that today. I have set the pilot air scews to the traditional 1-1/4 turn setting.

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