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  1. #1
    Policeman's Avatar
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    What have I've done now.......

    2003 Virage 700 Carb engine - Three week old engine from SBT in the ski and I took it out last night. For the first two hours it was bliss then I got a "Engine Overheat" message on my display. I killed the engine and took a look under the seat to find it filled with water. (up to the engine mounts) Long story short, I blew off a intake hose to the engine and the engine was sizzling hot. I assume that the water was not going to the engine which kept the sensor from catching it sooner. Water was literally sizzling on the jugs when I dripped on them.

    I bilged the water, connected the hose and after waiting for a period of time to cool, returned the ski to the trailer. It did run but not like it had been running.

    My question is this: SBT has a 2 year No Fault warranty as long as I do not open the jugs or the internal engine. So how do I check it for damage and did I just toast the engine? I plan on a compression check but besides that, I have no other idea on what to look for or how to check it without removing the top end..


  2. #2
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    DO NOT open the engine up if you do it's the end of the warranty. If you must get a borescope into the jugs for a look thru the plug hole. Do a compression check, if it's good, keep going, if not make arrangements for a warranty replacement.

    SBT covers anything you might have happen to an engine.

    You have some time left to blow up the engine, I'd suggest running the crap out of it from now on, you don't want it blowing up a month after the warranty is over.

    and folks..THAT is why I don't build engines. I can't guarantee ever hose on the ski..and when one lets go, it often means big trouble ( and not sinking either)

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  4. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Start with checking cylinder compression on the cold engine. All spark plugs out, strong battery, throttle held wide open.

    Record the numbers. Wait a few minutes, then check all the cylinders again.

    Put the plugs back in, run it dry on the trailer for maybe 30 seconds. This will warm the cylinders. Let it sit for a couple of minutes to distribute the heat. Then take all the plugs out and check compression again while the engine is still warm.

    All the numbers should be consistent, cylinder to cylinder variation should be less than 5%

    Hopefully the engine compression is still good.

    Before you do any further on water testing, review all the hose connections. Not only for tight hose clamps, but also that you actually have every hose where it needs to be. Sometimes swapped water hoses will allow the engine to still have cooling, just not 100% cooling. I have seen engines where the water feed and water exit hoses, which are the same size, have been swapped. If the thermostat is not installed there will still be water flow, it is just going through the engine backwards!

    Examine the rubber exhaust hoses for signs of overheating. If there are soft sections when you squeeze hard or you want to be sure, remove the large exhaust hoses and inspect them internally. Excess heat can cause the interior to delaminate and bilge inwards, restricting exhaust flow.

    Another test is to strap the hull to the trailer front AND rear. Back it down the launch ramp until the jet pump intake is submerged. Remove the seat. Now you can run it as long as needed while monitoring the engine for correct cooling, no water leaks, no exhaust smoke, etc. Make sure there is no debris or loose rocks under the jet intake, then you can apply throttle and see how the engine responds. Set the parking brake

    You should be able to put your hand on any part of the engine or exhaust for several seconds without burning your skin. This is true even after running at speed.

    Final test is to run it on the water. Monitor the maximum sustained RPM at wide open on smooth water. This tells you whether the engine is capable of delivering full power.

    If you test ride with the seat off you can monitor for unexpected water leaks, exhaust smoke, and engine temperatures.

    Sometimes the exhaust temp sensor can become damage by excessive heat, so you may need to replace it, just in case.

  5. #4
    Policeman's Avatar
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    K, I have just received my compression tester today and checked the cylinders as you suggested. Each cylinder is sporting 120 psi when cold and its almost unmeasurable difference when it was warm. I went through each hose and checked the clamps and studied the locations they were connected to. I did find a couple of clamps that were loose so I thank you for that. I will be heading to the water in a bit to do the trailer test and check for leaks.

    Quick question for you on the compression. My other ski with the same size engine pushed 150 psi in each cylinder. The difference is only a few years but had me scratching my head. I assumed that 120 was good for the new engine but why would the older ski have a higher psi? Could it be that this engine was bored out more?

    Thanks.

  6. #5
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    SBT is rumored to lower compression in their motors to try amd make them last longer. I do not know how much truth there is to this.

  7. #6
    Polaris John's Avatar
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    Seems kinda low for Polaris 700 twin, The engine has a one year warranty take for a ride see how it runs.
    I checked the compression on mine it was 142 on both cylinders the same day before a long ride and lost a cylinder that same day.

  8. #7
    Policeman's Avatar
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    I took it on a long ride (30 plus miles) at full rev and it tached out around 6500 rpm. I had to choke it slightly to get it to run smoothly but it did very well. Tomorrow I will check compression again and see where Im at. Does anyone else have a compression of 120? Love to know if this is normal for SBT engines.

    (photo is of my ride this evening)
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  9. #8
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    My 700 was never higher than 120 PSI. Compresion numbers relative to someone else's readings aren't a good comparison. Different gauges, elevation, cranking speed, battery strength all play a role. As long as they are consistent and even, and the engine runs well, dont worry about the number on the gauge.

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  11. #9
    any updates?
    I am considering an sbt motor for my 700.

  12. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Policeman View Post
    I took it on a long ride (30 plus miles) at full rev and it tached out around 6500 rpm.

    I had to choke it slightly to get it to run smoothly but it did very well.

    Tomorrow I will check compression again ...
    You needed choke to 'run smoothly' when? Cold engine, or after warming up? Does it need partial choke to run properly at speed?

    If it needs ANY choke to run properly once it has warmed up for a couple of minutes then the carburetors need adjustment.

    It is NOT a good idea to go for a long ride if the carburetors are out of adjustment, especially lean (needing some choke to run better).

    Lean burn engine damage is a real thing. It can happen quickly or it can happen slowly. It can happen at wide open throttle or it can happen at partial throttle. A lean running engine can seem to be running just fine when in fact it is eroding a hole into a piston.

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