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'95 SL750 Loss of Top End Power

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  • '95 SL750 Loss of Top End Power

    I am having trouble with a ’95 SL750 and need help. I inherited this ski last year and had about 12 hours on it when the trouble began.



    I had it out yesterday and it was running fine. I stopped the ski to drop of one passenger and pick up another. The ski started fine but had no acceleration and the top end and rpms were way down. When I got the ski home I replaced the spark plugs. I’m not sure of the numbering so I’ll call 1 the impeller end and 3 the front of the ski. 1 looked fine, 2 and 3 had a lot of carbon. The fuel filter was fine but I found a little rust-brown water in the fuel separator. I cleaned it out, added a water remover and topped off with 6 gallons of fresh gas.



    Today I took the ski out to run the water remover thru the system but the ski never ran any better. It started first or second crank every time and idled at ~ 1200 rpms. But again no acceleration to speak of and top speed was ~30 mph at ~4600 rpms. Again spark plug 1 looked fine, 2 had more carbon than I expected to see and 3 had almost enough carbon to bridge the plug gap. Also, there was more rust-brown water in the fuel separator (but isn’t that what the fuel separator is for?). Let me state here that last 2 times I got gas in my ski I also filled my truck and haven’t had any problems with it.



    I have read quite a few posts and have a good idea of what to check but wanted to post this incase someone has already been thru troubleshooting for a similar problem. I haven't check the compression, yet. Any help is greatly appreciated!
    Last edited by pseudonym; 08-07-2005, 09:37 PM.

  • #2
    Re: '95 SL750 Loss of Top End Power

    no doubt a little of that 'rust' got into your carbs. This could have lodged anywhere, in any jet, however probably has at least and maybe only, clogged the filters inside the carbs. You're gonna want to buy rebuild kits and rebuild those dudes. You could get in them and just check the filter, but after all the work of getting in there, if those carbs have never yet been rebuilt, you're going to want to rebuild them.

    Also, these ski's are notorious for not getting enough fuel. You'll want to purchase an add-on or replacement to higher performance fuel pump. Also, personally I bypassed the fuel shut-off check valve, mine was no good, and barely let enough fuel be pumped. If you use the stock pump, and it's not getting much fuel to the front cylinder, it could run lean and blow a hole in your front piston.

    While you're doing this work, you may want to consider going pre-mix, for that old oil pump, if it ever goes, you won't know it until it's too late.

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    • #3
      Re: '95 SL750 Loss of Top End Power

      Thanks surveguy, I hope that is the problem. Much easier than a holed piston!

      How hard is it to remove the tank to drain? Any advice for draining the tank without removing it?

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      • #4
        Re: '95 SL750 Loss of Top End Power

        I left my tank in, I think I unhooked the lines, fished the oil line out through the front, and down along side the ski, into my oil jug. It took a while, but I was in no hurry.

        You'll want to install a 33 ohm resister so your oil guage says full all the time. Just cut the two wires going to the tank, and solder or crimp in the resister between the two wires.

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        • #5
          Re: '95 SL750 Loss of Top End Power

          Update - I just did a compression check and here is what I found. These are not the absolute highest reading I got but are indicative of what I saw. These reading are with the engine cold as I really don't want to run it too much if there is a serious problem.

          Cylinder 1 - 95 psi

          Cylinder 2 - 110 psi

          Cylinder 3 - 110 psi



          Definitely not what I wanted to see but is 95 spin (16%) difference unreasonable? What would I expect to read if the piston had a hole (please don't say 95 psi)? Could the difference be a stuck ring? I do have a 'rattle' at idle that goes away with the slightest bit of throttle.

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          • #6
            Re: '95 SL750 Loss of Top End Power

            Time to pull the engine and tear it down - it's gone and needs at least a top-end job.
            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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            • #7
              Re: '95 SL750 Loss of Top End Power

              For my education:

              Would a hole in the piston cause the 95 psi? Would a stuck ring?

              Would whatever caused the 95 psi condition have caused the sudden loss of performance?

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              • #8
                Re: '95 SL750 Loss of Top End Power

                hole or no hole, you should have like 130# in each. We're not talking about 10 pounds here. Loss of performance? Heck.

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                • #9
                  Re: '95 SL750 Loss of Top End Power

                  I discussed the readings with the guy who lent me the compression gauge and he reminded me not to believe the absolute readings, just the relative readings between the cylinders. He actually told me that when I picked it up but I forgot. I'll have to get a better gauge and see what the true readings are.

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                  • #10
                    Re: '95 SL750 Loss of Top End Power

                    did you ever check the main fuel filter and water separator?

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                    • #11
                      Re: '95 SL750 Loss of Top End Power

                      Yes, the main filter was fine. I keep cleaning out the water separator but rusty looking water keeps collecting. Not enough to even register on the water level indicator but enough for me to be concerned. I drained the tank the best I could, I just need to get some time to pull it out and get the rest of the gas and drain the fuel lines.

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                      • #12
                        Re: '95 SL750 Loss of Top End Power

                        ok, too bad. You've got some work in front of you now, just in case you were bored :)

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                        • #13
                          Re: '95 SL750 Loss of Top End Power

                          Nooooo!! I don't want another project!!!

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