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  1. #1
    Piston? WHAT Piston?!? JGringo's Avatar
    Join Date
    May 2007
    Brookfield, WI/ Des Moine, Iowa/ Houghton, MI

    Ph2ocraft, Anyone, Help!!! 780 ignition issues!!

    I have come to the conclusion that I am doomed with broken jet skis... I have a 750 hull with a 780 motor and electronics in it. There is an extended pump, Rad flywheel, 785 carbs, and some other race type parts. I have replaced EVERYTHING mechanical. This includes... Top-end, bottom end, gaskets all around, flywheel, and carb rebuilds.

    My dilemma is that I have no real throttle response. I have a really weak spark from my spark plugs out on the lake, and the electrical box is not even fully sealed... I mean seriously I couldn't even see the spark from the plug. It would start but the response in the water was... well, to say the least, it was terrible. Out of the water it would rev up nice, like it is supposed to. I pulled the plugs after running them... well, bogging them out to the middle of the lake, and the front and back plugs were burnt like they wern't getting enough fuel and the middle looked like it got splashed with oil...

    I know that these pro 785 carbs worked fine before on this machine. I didn't mess with the jetting. I'd like to test the pop-off pressure but I don't know how and I don't have the tools...

    Another thing, I have access to an Ohms tester. Are the specs given in the tech area the right ones for the 780 also? Is it possible my spark plug wires are bad? If there is any water in the box whatsoever, will the box not work right? If so then thats probably why. You can actually see into my box

    But that cannot be the main problem... And where do I start with that? If the box really is the issue, can I fix it myself by going through and cleaning everything and then reassembling it? Are there any spark improving parts out there like MSD or something to make a much stronger spark? Is there any other possibilities that I am missing?

    I bought this ski broken. The back piston was burned real bad. I replaced the entire engine but the electricals.

    Ph2ocraft! Anyone! Help!!! I want to go out and Play!!

  2. #2
    ph2ocraft's Avatar
    Join Date
    Apr 2006
    Campbell, Ca.
    I have ONE question.
    Have you verified timing?

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    Did you cut about 1/4" off the plug wires and resecured the boots?

    Have you tested the coils with the ohm meter? PRO 785 coils are more voltage than 750 or 780 coils.

    Like Al said, where did you set the stator timing mark? Was it a 780 stator or the 750?

  4. #4
    Piston? WHAT Piston?!? JGringo's Avatar
    Join Date
    May 2007
    Brookfield, WI/ Des Moine, Iowa/ Houghton, MI
    I set the 780 stator to the stock settings. I aligned the line on the stator with the crankcase... I didn't retard or advance the timing in any way. If I cut the wires 1/4'' and test the spark, what will cutting the wires do? Do I cut them just on the plug connector end or on the other end (if possible). Are there replacement plug wires? Is there a possibility that the electronics just "went bad". The guy I bought it from said that was a possibility.

  5. #5
    Join Date
    Jul 2007
    Cedar Rapids,Iowa
    Just remove the boots and cut them back 1/4",It'll remove any corrosion were the wire is exposed.
    Take care of the Electrical box,Get it so it seals. Clean it all up,check for corrosion on the back side of the board and make sure connections are tight and clean, Also Do a check of the coils with the Ohm meter and make sure you don't have a weak one or bad one.

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