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Thread: sl780 troubles

  1. #1
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    sl780 troubles

    Howdy all
    This is what I know....The pto cyl is not firing. Compression on all cylinders is 115-120 warmed up. I've been through the carbs and fuel is being delivered to all cylinders. I've checked for spark and have it on all plugs. I'm thinking that its not firing during the compression stroke on the pto cyl.
    I've clipped 1/3 inch off of all plug wires, and even swapped plug wires and spark plugs between cylinders, and still only have a prob w/ the pto cyl. I was going to pull the grey wire,to see if its in limp mode, but its the only wire on the terminal. I was thinking that there should another wire to break the circuit from. I couldn't find continuity between that marked as "grey" terminal to any other to complete a circuit.
    I have ohm'd out the stator and all checks fine. I also have a problem w/ the tach on the mfd. 0 rpms when running. All other functions work. I've checked the yellow wire from cdi to the mfd, and checks ok. Do the 2 problems have something to do w/ each other?

    I bought this ski with these problems, and don't know if they happened at the same time.
    I suspect the cdi is my firing problem. Would it keep the tach from working too?
    Also, will a cdi from a 95 sl650 work in the sl780?


  2. #2
    Moderator beerdart's Avatar
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    That is a strange one if you swap the plug wires and still the PTO is a problem. All the coils fire at the same time they are in series.

  3. #3
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    I agree. I'm stumped. Will the cdi's swap? Well enough to see if thats the problem? I know the timing will differ a bit.

  4. #4
    ph2ocraft's Avatar
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    Check to make sure you don't just have the CDI wire hooked to the tachometer.
    You should have the green/red which goes from the coil to the CDI. The tachometer is tapped into that wire for the tachometer reading. Check for a broken wire, otherwise my guess is a bad CDI.
    Verify my wire colors as I don't have my manual with me.
    Last edited by ph2ocraft; 10-25-2007 at 06:24 PM. Reason: corrected component

  5. #5
    Moderator beerdart's Avatar
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    Yes the CDI from a 650 750 or 785 will wire up but the timing and rev limits are different.

  6. #6
    ph2ocraft's Avatar
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    On the miss to the rear cylinder check crank index. If you have spark, fuel and compression I'd guess it has to be timing.

  7. #7
    ph2ocraft's Avatar
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    Something else you typed seemed odd. The grey wire should go from the LR-54 to the CDI, you want to take that wire off the board. You're saying there is only one grey wire to the board?
    It might be somebody disabled the wire from the LR-54 to the CDI already?

  8. #8
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    Quote Originally Posted by ph2ocraft View Post
    Check to make sure you don't just have the CDI wire hooked to the tachometer.
    You should have the green/red which goes from the coil to the CDI. The tachometer is tapped into that wire for the tachometer reading. Check for a broken wire, otherwise my guess is a bad CDI.
    Verify my wire colors as I don't have my manual with me.

    The grn/red come from the stator and go to the cdi, and parallel the yellow to the mfd. The ign coils are wired to blk and blk/white from the cdi.

    Thanks guys.

  9. #9
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    Are the wire colors the same between the cdi's beerdart? I have'nt pulled the 650 apart yet.

  10. #10
    ph2ocraft's Avatar
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    Nothing is tapped into your green/red? Hmnnn, You may have just found the problem to this SLT780 I have here with no spark. I NEED my manual!!!!!!!

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