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  1. #1

    Advice on possible SBT warranty claim for low compression

    I installed an SBT motor a couple months ago due to the motor that was in my ski (03 Polaris freedom) having 90 PSI per cylinder compression. I checked compression when I first got the motor, and surprisingly, it only pumped like 100 PSI. I started to think I bought a motor for nothing, though I tried 2 other gauges before I bought this one. I also figured compression would go up with break in, which it did, slightly. I have had trouble tuning it just right on the low end. It always seems rich. Right now it sits at 111 and 114 PSI PTO and MAG respectively. SBT tests show my engine was at 130/130 before it shipped out. Here is the big question. Could this only be our difference in altitude? I am at 2600 feet and according to a scale I found, that would put each cylinder just over the 120 low end spec if I account for altitude. I don't know how much temperature plays a role, but that may be a factor too. Usually when I test, the Density altitude is more like 5,000. I am confident the gauge is not the issue as I walked out to a friends 01 seadoo GTX 782 RFI and it was 150/150. Can altitude be the issues or do I need to go ahead and get a new engine? SBT already started the claim but said they will do some more research first so I don't waste my time. I told them I don't want to pull the engine and then they test it at sea level and it meets the low end spec of 120. 120-150 may be Polaris spec for wear but it seems they should be on the higher end as fully rebuilt, not borderline, altitude as a factor or not.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    How many hours on this SBT engine now?

    What was your break-in procedure?

    What sustained RPM are you seeing at wide open on the water?

    Which impeller (part number) do you have in the jet pump?

    Have the carburetors been rebuilt? Genuine OEM parts?

    What carburetor jets and adjustment screw settings are you using?

    Have you inspected the intake reeds?

  3. #3
    ujustlost's Avatar
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    i know this doesn't hold true for all tools, but I bought my compression gauge from a local retailer and my buddy is a Volkswagen mechanic, I paid $29 for mine and he paid almost $500 for his from the snap on truck. We ran a check on one of my ski's and both gauges were so close it was hard to even tell if there was a difference, we had to take a picture of each one and compare them side by side to see the difference. My guess is your gauge is just fine. I am no scientist so I cant say weather altitude will affect a compression check. What caused the motor that was installed before this one to breakdown?

  4. #4
    Quote Originally Posted by K447 View Post
    How many hours on this SBT engine now? Guessing about 5-7.

    What was your break-in procedure? Exactly per SBT specs with their break in oil 32:1(Ski is premix also).

    What sustained RPM are you seeing at wide open on the water? No tach, just know it feels very strong mid range/ full throttle

    Which impeller (part number) do you have in the jet pump? Not sure on that either, I believe it is all original.

    Have the carburetors been rebuilt? Genuine OEM parts? Yes, genuine kit from John at Watcon, as well as the whole fuel system (pickup, line, selector valve).

    What carburetor jets and adjustment screw settings are you using? Bought new jets and went to stock specs, including the 1-3/4 turn out on low speed screw.

    Have you inspected the intake reeds?
    Also replaced these new from SBT.

  5. #5
    Quote Originally Posted by ujustlost View Post
    i know this doesn't hold true for all tools, but I bought my compression gauge from a local retailer and my buddy is a Volkswagen mechanic, I paid $29 for mine and he paid almost $500 for his from the snap on truck. We ran a check on one of my ski's and both gauges were so close it was hard to even tell if there was a difference, we had to take a picture of each one and compare them side by side to see the difference. My guess is your gauge is just fine. I am no scientist so I cant say weather altitude will affect a compression check. What caused the motor that was installed before this one to breakdown?
    I did my homework and knew to try different gauges the first time. I went through 3 total on the first motor and the other 2 matches this one. Then this one read good on the sea doo, so I am very confident it is reading correctly. Not sure of the original problem. Bought the SKI like that, I think it was lean. Jets were leaned out, it failed a leak down (front cover leak) and compression was low so I opted for the full SBT replacement.

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Hmm. Without a tachometer it is hard to say if the engine is actually developing proper power, for your altitude and air temperature.

    Compression while cranking is simply a proxy for estimating the engine's internal condition, primarily piston to cylinder wall sealing and compression ratio as defined by the combustion chamber volume. Sometimes an engine will measure compression that seems 'not quite right' yet it will run just fine and produce the expected power. Measuring compression at cranking speeds is a useful thing, but it is not the only thing.

    Polaris issued separate carburetor jetting and screw adjustments for 'high altitude' operation, but I do not recall at what altitude these applied.

    There were also high altitude impeller options, generally being a slightly lower blade pitch to avoid lugging the engine in the thinner air.

    Machines that were originally sold by a dealer located in a high altitude area could have come stock with the high altitude carb settings and impeller.

  7. #7
    I will probably order a tach soon. The jetting difference it did have was a 40 mid range instead of a 42 and a 135 main vs. 148. It seems to accelerate pretty well. Plugs were just very black and I think it is rich at low throttle. I did lower the lever arm spring to make 20 PSI pop off because that is what my manual calls for and I had no idea what someone did to the carb. I should get a new OEM arm/spring/needle kit later this week and that is the last thing I plan on trying before I go through the warranty process. Honestly, I am looking at getting a Genesis so me, the wife, and 2 kids can legally ride together. I just won't sell this to someone if it is not right.

  8. #8
    casey67's Avatar
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    How long is the hose on the compression tester ?

  9. #9
    Like 10-12 inches, the schrader valve is at the end of the hose though. Anyone know for sure what a 782 seadoo RFI should be? The gauge reads 150 on it.

  10. #10
    ujustlost's Avatar
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    Quote Originally Posted by 07keo02 View Post
    Like 10-12 inches, the schrader valve is at the end of the hose though. Anyone know for sure what a 782 seadoo RFI should be? The gauge reads 150 on it.
    I replaced the engine in my 96 seadoo challenger with a 787 sbt motor and compression was around 140 if I remember correctly

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