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  • #1

    Big problem

    Hey guys,

    I have an interesting problem that I need to proactively figure out before I sink more money and time into this thing (1996 Polaris SL780). I purchased a rebuilt engine from SBT couple of years ago. Ran fine for the summer, but when I took it out last summer, I lost the number 3 cylinder. It was still under warranty and they replaced with no hassles. When I received new engine, they sent me a reason why the other failed and was due to "pre ignition which results from running reg unleaded gas or incorrect spark plug". Installed new engine, made sure to put in correct spark plugs and ran only high octane (93) through it. My wife decided to run up on a log and punch a nice hole in it last year after about 7 hours on new engine, so I put it up for the year. Fogged the cylinders and sat in garage until last week. Fixed the fiberglass, put new gas, and new plugs in it (again, making sure to use only what it calls for) and rode it last week. Ran great for about 3 hours and then lost power. Pulled plug off number 3 and again no compression. Removed the head (since no longer under warranty) and I burned a hole straight through the piston. Before I rebuild, does anyone have any idea how I continue to burn pistons. Premixing oil (Quicksilver-PWC Oil) 40:1. Any ideas?

    Thanks
    Tags: None
  • #2
    Re: Big problem

    If it ran fine until you put it up and died right after you took it out, the fuel was probably simply too old to use. Octane degrades after only a few months.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

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    • #3
      Re: Big problem

      Well, the only problem with that is, I had to remove the tank to repair the fiberglass. I emptied the tank and rinsed it out really good with fresh gas before refilling with premix. Anything else you can think of??

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      • #4
        Re: Big problem

        A clog in the fuel system, lines hooked up backwards, clogged filters, water in the fuel, carbs misadjusted, airleak...
        SBT Tech Support is here to help with your problems.
        We try to answer each question quickly and accurately.
        Please do not use Private Messaging for Tech Support, use the forums.

        Comment

        • #5
          Re: Big problem

          I was actually leaning toward the number 3 carb running too lean, but wanted to get a professional opinion. What can I do to verify the correct fuel/air mixture? Thanks for your help.

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          • #6
            Re: Big problem

            Before hand, all you can do is make sure your equipment is working correctly - carbs are rebuilt, lines are correct, gaskets are sealing, pressure test the block, etc. During running you can check the plugs but that can be hard if it's burning down quickly. Other than that it takes expensive mods like EGTs.
            SBT Tech Support is here to help with your problems.
            We try to answer each question quickly and accurately.
            Please do not use Private Messaging for Tech Support, use the forums.

            Comment

            • #7
              Re: Big problem

              Forgive my ignorance, but what are EGT's?

              Comment

              • #8
                Re: Big problem

                Exhaust Gas Temperature probes.
                SBT Tech Support is here to help with your problems.
                We try to answer each question quickly and accurately.
                Please do not use Private Messaging for Tech Support, use the forums.

                Comment

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