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  1. #1

    New SLX 780, did suggested maint, still problems....

    Hey Everyone....

    I posted a while back about a new SLX 780 that I bought (well new to me anyway) and what maintenance I had to do to get her to turn over after sitting for a while.

    I followed XLINT's advice and rebuilt the carbs, replaced the battery and replaced all the fuel lines. Also scrubbed the gas tank clean and cleaned all fuel valves, gas water separator, etc.

    Turned her over in my garage after all this work was done and she started right up. Seems to run great. Ran for 10 seconds before I shut her off.

    Dragged it out to the lake and put it in the water, again started right up.

    I let it sit for 3 minutes idling and finally got on and started to give it some throttle. BAM. Dead. Thankfully I had a buddy with me, towed me back to the dock. Sat for 3 mins, turned it over again and started up. This time, got a little further. Gave it some throttle and took off right away. Half throttle maybe (wow...this thing was a little more ballsy than I expected) but within a minute, dead again.

    This time brought it back to shore and couldn't get it started. Turns out the reset switch on the ECM (computer box?) had been tripped and wouldn't allow it to turn over) - figured this out after I got it home again.

    Anyone have an ideas? I was running 89 octane and didn't even think that it may require a different octane. I can get it to turn over in my garage again, no problem. But the throttle seems to kill it?

    Thanks in advance....

    Dying to get on the water!

    -chicagoanalog


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Does the electrical box sit on top of the battery?

    If so, is the plastic cover for the battery missing?

    The electrical box must NOT touch the battery posts.

    When you did the other work, did you check inside the electrical box? Should have zero moisture, no corrosion, and no loose connections.

    Check again for damage wires. My suspicion is that the electrical box may be shorting somehow. Either something inside the box, or the box itself touching the battery...

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Well that's a bummer.

    When you say bam, dead. Does it sputter or just crap out?

    Are you cruising along and it just dies?

    Did you hit any waves then die?

    If the circuit breaker is tripped you had a short. Do you have the black plastic cover over the battery to insulate if from the metal elec box?

    Was the engine hot to the touch?

    Was the MFD red light blinking and displaying anything?


    Yeah, you will be happy with that ski. It should do about 54 MPH and get there rather quickly.

  4. #4
    Quote Originally Posted by K447 View Post
    Does the electrical box sit on top of the battery?

    If so, is the plastic cover for the battery missing?

    The electrical box must NOT touch the battery posts.

    When you did the other work, did you check inside the electrical box? Should have zero moisture, no corrosion, and no loose connections.

    Check again for damage wires. My suspicion is that the electrical box may be shorting somehow. Either something inside the box, or the box itself touching the battery...
    There is a plastic cover over the battery. Inside the box, it's free from moisture / corrosion, etc. Looks brand new in there.

    I should be clear that I am "assuming" the breaker was tripped. Wouldn't start in the water but once I pulled it out and tried to to turn it over on the trailer, it wouldn't start either. Then when I got it back to the garage after trying again, nothing. Hit the reset button and started right up.

    I was thinking fuel issue instead of electrical. Like once it gets too much fuel it bogs and dies.

    There was one interesting thing I saw about the fuel hose routing. It has had the triple output upgrade (breaking off to each cylinder individually). But the return line from the rail back to the tank....it's just a plug. The hose runs from the return line rail back to the tank. But at the rail, it's not a barb....it's actually just a solid plug shaped like a barb. Is this right?

  5. #5
    Quote Originally Posted by xlint89 View Post
    Well that's a bummer.

    When you say bam, dead. Does it sputter or just crap out?

    Are you cruising along and it just dies?

    Did you hit any waves then die?

    If the circuit breaker is tripped you had a short. Do you have the black plastic cover over the battery to insulate if from the metal elec box?

    Was the engine hot to the touch?

    Was the MFD red light blinking and displaying anything?


    Yeah, you will be happy with that ski. It should do about 54 MPH and get there rather quickly.

    Tell me about it. I was really excited to get out there.

    When it dies....it sputters out. Which was making me think it was a fuel problem. If I ease off the throttle, the combustion is salvageable (if that makes sense). I can keep it at idle for a little while. Again, this was making me think it was a fuel issue. As I mentioned above, the return line seems to be stubbing out from a plug shaped like a barb (there is no outlet / return back to the tank), unless this guy had it plugged in at the wrong place.

    I do have the cover as I mentioned. Engine was warm but not scolding or anything. Definitely not enough to make me think it was overheating.

    MFD is a little foggy but still functional. Didn't say anything but flashes red when I was trying to turn it back over though if I'm not mistaken, this is normal right? Should flash for a minute than go off.

    It was lake michigan so it was a little choppy but not too bad. Dying didn't seem to correlate to the waves but who knows.

    Im wondering if maybe that breaker wasn't even tripped and it starting again was just coincidence after letting it sit for a few.


    Man, 90 degrees and gorgeous today. I never thought a 2 stroke could give this kind of head ache.

  6. #6

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    If it was cranking and not starting then the beaker did not pop .I would pull the fuel on/off switch to see if it's clogged up ,it was a commom problem on those machines

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by chicagoanalog View Post
    ...
    There was one interesting thing I saw about the fuel hose routing. It has had the triple output upgrade (breaking off to each cylinder individually).

    But the return line from the rail back to the tank....it's just a plug. The hose runs from the return line rail back to the tank. But at the rail, it's not a barb....it's actually just a solid plug shaped like a barb. Is this right?
    That does not sound corrrect.

    Can you post clear photos of how the fuel lines are connected to the carbs? Both feed and return.

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    OK, it does sound like a fuel issue thus far.



    The return hose should NOT be plugged. It should actually return to the gas tank unobstructed. Your restrictor is built into the carb rack, so plumb the hose directly from the carbs to the fitting on the fuel sender.

    Running WOT will create alot of fuel pressure, and if it can't return to the tank it's going to back up into the carbs and act like a "flooding" condition, causeing it to bog down and die. Next time this happens, remove a spark plug (take a wrench with you) and see if the plug is wet.

    Not a bad idea to disassemble the petcock as Lugs mentioned. You can see if there's any restriction inside the valve. The most common issue is the rubber seal starts to swell and closes the opening, decreasing the fuel supply.

  9. #9
    hmmm... it is a fuel problem when you try to rev it and dies.... i have the same problems on mine 1st start in the morning.. but it will disappear after 2 mins...when the fuel pressure will be stable already...

  10. #10
    Quote Originally Posted by K447 View Post
    That does not sound corrrect.

    Can you post clear photos of how the fuel lines are connected to the carbs? Both feed and return.

    Sorry for the delay, these are the best photos I can do without taking the carbs off.

    If you look, you will see the brass barb shaped "plug". To be clear, this is not an outlet, despite the fact that the return hose attaches to this.

    Individual fuel lines from the fuel pump go to each one of the cylinders. Then above that, there is a fuel line that just seems to go from cylinder to cylinder and end in that plug?

    Really confused. I am assuming that I MUST have some sort of return, right? Otherwise it's gonna flood.

    Let me know if I need to take the carbs off for a better shot of the fuel line routing.

    Appreciate the advice.





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