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  • SL 750 Polaris

    What effect will the wrong oil pump block-off plate have on engine performance? I used a flat plate with no plug.

  • #2
    I am still having a problem with ski running out of fuel. I have tried running it on and reserve settings. I checked and tightened all fuel lines, no kinks. I checked fuel tank vents, and they are o.k.. Now the ski did not have this problem before I pulled the carbs. I didn't change anything, just pulled covers, diaphrams, and cleaned out some small pieces of trash in the high speed circuit of one of the carbs. The other two carbs were clean with no problems. The ski only set for a week after pulled the carbs and put it back together. I have tried everything. The fuel pump is a new mikuni high flow with two outlets. What could I have done during carb cleaning that would cause this problem? I am stumped. Please help.

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    • #3
      I'm running without the plug, just the plate. It is a sealed chamber... i'll take the gamble that it doesn't really matter.

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      • #4
        Ok... did "everything" is hard.

        Could you be pulling air into the lines from a bad connection?

        Are you using the old fuel lines? New fuel lines? Zip ties on everything, screw clamps, or just friction fit?

        How do you have the fuel routed on your new carb setup?

        and finally... what makes you think you are running out of fuel? Are you SURE that you are not running too rich? Just a thought.

        -Skexies

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        • #5
          skexies, thanks for the reply. I haven't changed any of the fuel lines. I did check for the restricter in the return line and found that it was clogged. What effect would this have? The ski doesn't seem to getting enough fuel and the plugs show no signs of flooding, fouling, or being too rich. The clogged return doesn't seem like it would cause it to run out of gas but I know I may be wrong about that theory. Have you ever installed extra fuel pumps? If so how and where did you plumb the lines. I made this modification to the 93 sl750 which I discussed in the general discussion section on this site. I plumbed the thing exactly the way SBT's paper said to, but the ski would not run properly with it installed. It basically did the same thing my ski is doing now, running out of gas.(or at least that is what it seems like)Any info or tips on the 750's would be greatly appreciated. My MFD(multi-function display) went bad, do you know where I may be able to get a used one. Polaris wants $280 for a new one. Thanks for the help.

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          • #6
            OK, isolate the issue. Running out of fuel idling? 1/2 throtle, full? I'd double check spark plug types/end gaps as well. ;)

            I went out to the parts store and bought a long roll of 1/4" fuel line and a bunch of small screw clamps. The old hoses on this boat were so hard that I know they did not seal well. You might want to do that as well... it is not very costly and would help eliminate leaking lines as a problem.

            If you don't run with the second fuel pump, I'd have to ask how you routed the fuel returns / feeds / and pulse lines. Previous owner of my boat had the fuel supply line doubled back on itself, so it kinked off a bit. :( Here is a pic of it... you can also make sure you have the correct lines. At first guess... I would expect a mis-routed fuel line ;) How do you have the dual fuel outlets run?
            http://fcm.teq.org/business/projects...inked-fuel.jpg


            I would suggest you route fuel from the pentagonal pump like this... using two 1/4" brass tees [but this is just my openion] http://fcm.teq.org/business/projects...el-routing.jpg

            While apart, did you clean the little filters in the carbs as well?

            Sorry, dunno about the MFD... perhaps check various salvage companies like M&M or something.

            Lemme know,
            -Skexies

            [ April 30, 2001: Message edited by: Skexies ]

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            • #7
              Skexies, Thanks for the pics and info, I am going to try the fuel routing. I went back into the carbs this weekend and rechecked everything. I found a clogged orifice in the third carb coming from the fuel lines in. O.k. now I'm not running out of fuel anymore but I have another problem. The ski accelerates to wide open and then after 5 to 10 seconds the rpm's drop back some. It seems to lose it's *** somewhat. Now it probably only drops back 1000 rpm's or so. I was thinking a low oil or fuel indicator would drop it back more. I checked them about a month ago when I was troubleshooting the other problem and they were o.k., but this was before my M.F.D took a **** . Now I don't have a oil tank. I just used a zip tie to hold the sender up at full position. Can I just unplug it from the box or does it have to be hooked up? Can you think of a problem that could cause my rpm problem. I can't tell if i still have a fuel delivery problem or if I am now dealing with something electrical. Thanks again for the help. Jay

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              • #8
                I'll let you know in the next day or so if you can just jumper the oil sensor leads. I was about to do that to mine, but I have not got the time.

                check out www.groupk.com they have some good articles on carb tuning...

                "With the engine well warmed up, bring the boat quickly up to peak rpm and observe the peak rpm numbers. With a perfectly set high-speed screw, the tach numbers will peak out, then fluctuate up and down within a 30-rpm range. If the mixture is lean, the engine will accelerate strongly up to peak rpm, and then begin to descend steadily without ever stabilizing or raising back up. This situation requires some judgement with respect to the rate of rpm decline. If the rpms decline at the rate of 10 rpm every 5 seconds or longer, the lean condition is slight. If the rpms decline at a rate of 10 rpm every 2 seconds or faster, you have a severe lean condition that can result in seizure if the run is sustained. No matter what the rate of descending rpms, after a loss of 50 rpm or more, the risk of seizure becomes very real. The full throttle pass should be stopped, and a richer setting should be tested."

                Take care,
                -Skexies

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                • #9
                  Thanks for that info, that is exactly the way it is acting. I have still not located a MFD so I'm not sure about the rpm's but just listening to it I can tell. It seems to me you have been around alot of Polaris jet ski's. How many MFD's have you seen go bad? Mine had gotten hard to read before it finally went completely. I like having it but the $290 price tag is more than I want to spend. I just want to get it running right and sell it. I've got more money in it than I ever wanted to spend. I should have bought a new one!!! The only reason I bought it was because it looked flawless, but I only rode it 3 times before the motor slung a crank bearing. Another question if you don't mind, How do you set the timing up when you are changing the engine? Do you uses the marks on the stator lined up with the casting on the block? This is how I was told to do it, but I have wondered if there was a more accurate way. Thanks again for the info. Jay

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                  • #10
                    Skexies, just wanted you to know I fixed my ski. It was definetley running too lean. I rerouted the fuel lines a different way and it solved the problem, why I don't know. I could not believe it but the ski ran 53 mph(according to my new MFD???) and it was running about 63-6400 rpm's. I know this may not be accurate but still the same I was quite amazed. Before I replaced the engine it would run about 49-50. Thanks for the help!!

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                    • #11
                      Me and two friends all got either SL750's or SLXs in 95 and 96. So far we have went through 10 MFDs on the three. They either fill up with water or fade out. That's on top of two melted pistons on my SL750 and one thrown rod on the SLX. I think I was a pioneer on the added fuel pump fix :D . I liked the way the SL750 looked and rode but I now have a Kawasaki.

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