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  1. #1

    96 SLT 700 power loss, has new ignition system

    I have noticed there are several 700's on here that upon warm up or after 20-30 min. that they lose power. This is exactly what my 700 did last year everyone said its ALWAYS ignition and I had jump started it that day,so I thought maybe I fried the stator. long story short I did the whole ignition system upgrade, finally got around to the water test and same symptoms exist. Starts out fine, after a while(time seems to vary) then it starts out bogging only at WOT, as time progresses it gets worse and worse meaning you go slower and slower until it only idles and eventually it will die. Once engine cools seems fine. SO, I have all new ignition system, compression is: 125/122 which I believe is satisfactory. this leaves me at fuel. IS it possible this thing is overheating or is the cooling system foolproof? Seems to be good flow of gas from tank to water separator cup both in on and res positions....any suggestions? OOOH I ALMOST FORGOT I have a friend that swears it is because of possible 2 cycle oil mix. I always used Polaris oil but I have no idea what specific oil was in the ski, but I stopped at Polaris dealer and got synthetic polaris 2 cycle. Friend swears thats my problem. Current status Fuel tank out , clean , dry. Needed a new fuel float anyway. Oil tank out clean, dry and ready for new. Any help appreciated as always. Also since I did the upgrade and have the same symptoms I guess I have a Working factory ignition system if anyones lookin. Also sounds like maybe worth replacing impulse line, worth a shot anyway


  2. #2
    o
    Last edited by vortecsix; 01-17-2011 at 08:25 PM.

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    For some reason I did not see your new thread when you posted it

    As you can see this forum is fairly active, with numerous threads in progress and new members questions. When you didn't get a response after a few days, the usual action is to post a short message in the thread to bring it back to the top of the list.

    To answer some of your questions;

    The cooling system certainly could be a problem. It is easy enough to check. The engine should never get so hot that you cannot put your hand on any part of the cylinders or exhaust system. Normal operating temperature is about 140F, which means you should be able to hold your hand on it for 2-3 seconds without burning yourself.

    If you cannot touch a cylinder head or exhaust manifold then there is a problem with the cooling water flow.

    Check the water inlet inside the jet pump exit nozzle (right side when looking from the rear). Make sure that plastic mesh screen is clean and clear. Might need to use a small mirror to see it.

    Remove and check the thermostat housing. Look for clogs or other problems. Make sure the pressure by-pass plunger valve is not sticking. If you have a thermostat you can check it in a pot of water on the stove. Slowly heat the water while watching the water temp on a thermometer. Thermostat should open around or just above 140F.

    TC-W3 rated oils should be compatible and mixable, regardless of brand. An oil failure would result in significant cylinder wear and damage, so the engine would not run properly afterwards. Compression is reduced when lubrication is poor, so the engine would deliver less and less power if the oils were not lubricating the engine.

    Since your compression numbers are even and within reason I doubt oil is the problem.

    What work have you done on the engine, other than the ignition system upgrade?

    Carburetors taken apart, internally cleaned and rebuilt?

    Fuel hoses changed, new fuel filter?

    Fuel tank venting. When the problem happens, stop the engine, crack open the fuel filler cap. Do you hear a strong hiss of air pressure? Close the gas cap and ride again. Did the problem go away? If yes, one or both of the fuel tank venting check valves is stuck closed. Replace both check valves.

    Since you have the fuel tank out, now would be a good time to change the two venting check valves. Make sure you install each valve (they are different) in the correct location and orientation. They are one-way valves, and must be installed correctly.

    Another thing to check for is exhaust gas leaks into the hull. Check all clamps and exhaust hoses for looseness, bulges, or softness. Feel around behind and under each hose. If the exhaust water injection is not working properly the rubber hoses can get too hot and fail.

    When riding, if the problem happens again take the seat off and test ride. With the seat off the engine air intake can get fresh air even if there is an exhaust leak. If taking the seat off makes the problem go away then hunt for an exhaust leak.

    Make sure the mesh screen and orifice for the exhaust water injection are both clean and clear. Do not enlarge the orifice, just make sure it is not clogged. Use the online parts diagrams to find where these items are on your engine.

  4. #4
    Thanks K447, Its been awhile since I've had the chance to play with the ski, but I left it at this: I removed / drained fuel and oil tanks. All valves were flowing easily and properly, Vaporlock was one of first thoughts, sometimes when I remove fuel cap , the has slight positive pressure, if it sits in the sun I can hear pressure relief valve releasing pressure. As far as I know, motor is completely original and untouched, maybe carbs too?!? I bought the ski in 05 and this started in 09, it gets run sporadically , so gunk in the carbs is not out of the question, but in my experience , carbueration issues are usually much more consistent, not just after 20 min or whatever. Especially, it runs perfect when its cool, with the new ignition it actually felt more responsive and eliminated a studder on take off. That being said, I have not had a chance to inspect cooling system as recomended, but I will , promptly, also I will inspect the exhaust. I did replace the impulse line as it did seem to have a "semi-soft" spot in it, I was hoping that was the culpurit. I'm hesitant to water test it though, plus I figured it good to sit dry of all petroleum for the winter-thanks tom

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by vortecsix View Post
    ...sometimes when I remove fuel cap , the has slight positive pressure, if it sits in the sun I can hear pressure relief valve releasing pressure.

    As far as I know, motor is completely original and untouched, maybe carbs too?!? I bought the ski in 05 and this started in 09, it gets run sporadically , so gunk in the carbs is not out of the question, but in my experience carburetion issues are usually much more consistent, not just after 20 min or whatever.

    Especially, it runs perfect when its cool, with the new ignition it actually felt more responsive and eliminated a stutter on take off.

    ...I have not had a chance to inspect cooling system as recommended, but I will , promptly, also I will inspect the exhaust.

    ...I'm hesitant to water test it though, plus I figured it good to sit dry of all petroleum for the winter-thanks tom
    The fuel tank normally does maintain a slight positive pressure, about 1-2 PSI. The venting check valve releases an pressure above this level.

    Draining the fuel tank is fine for storage, but is not really necessary. Same for the oil tank.

    I would agree that the carbs could be the problem, or part of it. If it was mine I would be doing a carb cleaning and rebuild, just to be sure. Sometimes you find surprises when you get into them.

    A useful water test method is to keep the hull well strapped to the trailer front AND rear. Back it down the launch ramp until the jet pump intake is well submerged. Now you can run the engine as long as you like, while standing beside the machine on the trailer. You can test with the seat on or off, and check temperatures easily while the engine is running.

    You can even apply throttle. Just make sure it really is well restrained to the trailer, and the ramp is free of small rocks and loose stuff that could get sucked into the pump.

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