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  1. #1

    1996 SLT780 revival -- couple tech questions

    I've revived my 96 SLT780 after it sat for many moons and it seems to be doing better than I expected. I've replaced several items that needed attention and have taken to the water a couple of times to shake it down, so to speak. I've got a couple of concerns though, namely:

    -- Fuel. As I understand it, this model has a 3-outlet fuel pump so each carb has its own fuel supply. Is this pump a source of problems and does anything need to be addressed to keep it running reliably? Is the fuel selector switch a source of problems? I seem to recall reading that some of them were a potential restriction and could cause a lean condition but I'm unsure of what models/years that affected.

    -- Carbs. These need to be tuned. It dies every now and then at idle but I suspect that's a simple idle adjustment. The engine stumbles pretty badly at around 5000 RPM more often than not. I don't notice a correlation between how long I've been idling/going slow before giving it WOT when this happens so could it just be the high speed mixture that needs adjustment? It isn't fouling the plugs any more than I remember so I'm assuming this is indicative of a lean condition? My carbs have a little black knob with a small pin through it (forming a sort of a T) and a little brass knob on the other side. Which is the low speed and which is the high speed adjuster? (When this problem occurs I back off the throttle in hopes of preventing damage).

    Thanks!


  2. #2
    xplayer2885's Avatar
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    First off welcome to the hulk!!!! The fuel selector nob is a source of problem. It leaks, you can either take it apart an rebuild it, or get one from seadoo. I forgot the part number but i can look it up for you after.

    Now for the engine killing out on you at idle, whats your idle speed in the water? Your also saying that that at 5k the engine is running iffy? With the age of the machine i would take the carbs apart clean them, an inspect all the rubber. Carbs are very simple to rebuild, an you can find the rebuild kits for around $43 each. Every thing comes with them. I would also replace all of your fuel lines are well, becuase they are prone to cracking an tend to have air leaks. Also if you can pull out the sending unit in the tank an see if theres any shit stuck up in the sending unit. I would also replace your fuel filter. Hope this is a good place for you to start!!!

  3. #3
    Thanks for the welcome!

    Luckily, my selector valve does not leak but I am concerned after reading that some were a source of fuel restrictions. I checked all of the fuel lines carefully before I started working on it a few months back and they seemed to be in good shape but I do plan to replace them anyway -- no telling what the condition of them is inside.

    As for the fuel sender -- I took a look at it when I replaced the fuel level float and it looked OK so I didn't do anything to it. Idle speed in the water was about 1100 and bobbled slowly downward at times. I understand it should be around 1250 or so -- hopefully the idle adjustment screw will take care of that.

    Good advice on the carbs -- I'll probably break down and have someone service them as I know a lot less about them then I'd like to.

  4. #4
    Wankel till I die!! jonjonwells's Avatar
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    If you have anyone service them, I would highly recommend Randy at Watcon. He did my 44's for me and did an amazing job. Very competitive pricing and quick turnaround.

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by RAdams View Post
    ...my fuel selector valve does not leak...
    Just to be clear. When they get old the fuel selector valves tend to leak air into the fuel lines, not fuel out. The fuel lines from the tank up to the fuel pump are under suction, not pressure.

    Air in the fuel makes for uneven and lean burn engine operation, and makes carburetor tuning impossible.

  6. #6
    BBCaprice's Avatar
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    Quote Originally Posted by RAdams View Post
    I've revived my 96 SLT780 after it sat for many moons and it seems to be doing better than I expected. I've replaced several items that needed attention and have taken to the water a couple of times to shake it down, so to speak. I've got a couple of concerns though, namely:

    -- Fuel. As I understand it, this model has a 3-outlet fuel pump so each carb has its own fuel supply. Is this pump a source of problems and does anything need to be addressed to keep it running reliably? Is the fuel selector switch a source of problems? I seem to recall reading that some of them were a potential restriction and could cause a lean condition but I'm unsure of what models/years that affected.

    -- Carbs. These need to be tuned. It dies every now and then at idle but I suspect that's a simple idle adjustment. The engine stumbles pretty badly at around 5000 RPM more often than not. I don't notice a correlation between how long I've been idling/going slow before giving it WOT when this happens so could it just be the high speed mixture that needs adjustment? It isn't fouling the plugs any more than I remember so I'm assuming this is indicative of a lean condition? My carbs have a little black knob with a small pin through it (forming a sort of a T) and a little brass knob on the other side. Which is the low speed and which is the high speed adjuster? (When this problem occurs I back off the throttle in hopes of preventing damage).

    Thanks!
    Black knob w/ pin- low speeds. Brass looking screw- high speeds. Check and see where they are. Should be about 1 1/2 turns out on mag & PTO and 7/8 out on CEN.

  7. #7
    Thank you all for the tips and advice -- I really do appreciate the information.

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Do you have any modifications to your ski?

    Your fuel pump is the preferred triple outlet. If you have concerns about it, it can be easily rebuilt for around $12.

    Fuel selector valves are a source of restriction. You can easily clean/inspect it.

    Before trying to adjust the carbs, you should clean/inspect them. They are pretty easy to do yourself. You can buy just the parts you need vs. the rebuild kits. They have alot of parts that your carbs won't need, plus they don't have the new needle and seats.

    If you have a brass adjustment screw visable, someone has adjusted your carbs from factory settings already. The factory puts a limiter cap on them to keep people from messing with the adjustments.

    If your ski is stumbling at WOT, DON"T RUN IT WOT!!!!! You are most likely starving for fuel and causing piston damage. CLEAN your carbs.

  9. #9
    BBCaprice's Avatar
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    If you have a brass adjustment screw visable, someone has adjusted your carbs from factory settings already.
    The factory puts a limiter cap on them to keep people from messing with the adjustments.
    Thats the first thing to go, isnt it?

  10. #10
    Quote Originally Posted by xlint89 View Post
    Do you have any modifications to your ski?

    Your fuel pump is the preferred triple outlet. If you have concerns about it, it can be easily rebuilt for around $12.

    Fuel selector valves are a source of restriction. You can easily clean/inspect it.

    Before trying to adjust the carbs, you should clean/inspect them. They are pretty easy to do yourself. You can buy just the parts you need vs. the rebuild kits. They have alot of parts that your carbs won't need, plus they don't have the new needle and seats.

    If you have a brass adjustment screw visable, someone has adjusted your carbs from factory settings already. The factory puts a limiter cap on them to keep people from messing with the adjustments.

    If your ski is stumbling at WOT, DON"T RUN IT WOT!!!!! You are most likely starving for fuel and causing piston damage. CLEAN your carbs.
    I have aftermarket flame arrestors, a single scoop intake grate and a TDR waterbox. The carbs were adjusted many moons ago (by my dealer) for these mods. I suspect they never reinstalled the limiting caps.

    It was running very cleanly for the first 10 minutes or so, including a few blasts to WOT. Once the stumbling started, I immediately backed off and ran very slowly for the rest of the ride. I didn't have an extra set of plugs on me at the time or I'd have pulled them right then and tried to read them. As they sit, they're definitely now showing signs of a lean condition but that's after much low speed riding (where it incidentally has no stumbling or performance problems).

    I do plan to clean up the carbs. I'm mechanically inclined but have never worked on a carb (other than to stop a lawn mower I once had from puking fuel out of the breather hole in the primer bulb). I'll probably just buy the rebuild kits since I'm not sure which parts are an absolute necessity to replace and which can stay.
    Last edited by RAdams; 04-07-2008 at 09:48 PM.

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