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Thread: SLT 780

  1. #1

    SLT 780

    I've acquired a 96/97 SLT 780 and have very limited knowledge of jet skis. What I do know is that the steering cable is froze, and the ski will start by spraying starter fluid into the carbs but will not run. Compression is 155-160 on all three cylinders so that seems good. I've pulled the carbs and installed rebuild kits including new needle valve and seats. When I went through the carbs, two of them were full of oil, to the point the needle valve was stuck on the seat. Before putting the carbs back in I wanted to verify the fuel pump was working so I turned the motor over but didn't see any fuel coming from the fuel lines. So question is, what drives the fuel pump? I'm assuming crank case pressure. So by not having the carbs installed on the intake did that prevent enough crank case pressure from turning the fuel pump over?

  2. #2
    Click avatar for tech links/info K447's Avatar
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    Jul 2007
    near Toronto, Canada

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  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    Welcome to the Hulk.

    155-160 is kind of hi compression. I'm wondering if the previous owner fogged the engine for extended storage and is the reason for the slightly higher compression reading?

    Yes, crankcase pressure is what drives the fuel pump diaphragm. Proper way of testing the fuel pump is to install a vacuum pump on the pulse fitting and apply a light vacuum to it. It should hold indefinitely. If it doesn't, there's a leak.

    It takes a while for fuel to be drawn through the fuel lines from the tank. It's best to prime the engine with premix gas down the carb throats, as that will get the fuel flowing much faster with less stress on your battery and starter.

    It's not recommended to use starting fluid. It may wash the oil off the cylinder walls.

    I'm not sure where you're located, but if the steering cable is frozen, my guess is salt water. If that's the case, look closely at the wear ring to impeller clearance as well. A lot of times the SS liner bulges from corrosion between it and the aluminum housing. Or it can be pitted causing excessive clearance between it and the impeller.

    First, get them running. Then worry about the steering/propulsion

  4. #4

    First, get them running. Then worry about the steering/propulsion
    Yeah thats the plan. I have a vacume pump that I will connect to the pulse port of the pump to check the diaphragm. Also plan on making sure the fuel on off valve is working and not restricting flow. All of the oil just sitting in the carb has me wondering if there is any fuel getting to them. Any idea where I can download a service manual? I've seen a few post with people directing others to their Avatar for manuals but I was unable to find them.
    Last edited by K447; 01-25-2020 at 02:27 PM.

  5. #5
    Well pulled a small vacuum on the fuel pump and it held so I assumed it was good. Replaced all of the fuel lines, installed rebuilt carbs, set needle valves to factory settings, installed carbs, bi-passed the fuel shut off valve, cut the plug wires back 1/4", and low and behold it came to life. Only ran it a 20-30 seconds and it smokes like a train, so Im hoping who ever had it last put it up for the winter by fouling it and there it sat for years. Hopefully I can bring it to water tomorrow and run it on the trailer. I guess the next step is to figure out if the pump is in good enough shape to continue on with getting this thing water ready. The owners that had it did live in a brackish water part of the state so it did see salt water.

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    Most likely the oil in the carbs was oil and gas mix, but the gas evaporated over time, leaving just the oil.

    These blue Fuji engines are quite reliable. The weak point is the fuel system. Keep that in top notch shape, and it will run for a long time.

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