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  1. #1

    Join Date
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    HELP- no power internal damage

    On the 95 750 I think I just discovered I have an expensive problem. Please excuse the wrong terminology and long explanation. You guys were probabley right on with the internal damage.

    I just ran it on trailer with flush kit hooked up to look for obvious leaks etc. Did not see any but then I decided to pull the plugs to change and noticed steam coming out of 1st 2 holes but not the 3rd (back end). I shined a light in all 3 and could see what looked like a round hole with more shiny metal presssed in(seemed normal) I think this is the top of the cylinder head. However, in the 3rd one the shiny metal is not there making it flush and smoothe and there is actually a hole that you can stick a screwdriver in. It looks to me a machined hole with something missing.

    Heres the part where I think I am screwed for sure. The normal looking cylinders have the shiny part lined up with the center of the plug hole. The 3rd does not. It left of center.

    When listening to it run it kind of sounds like a old 2 stroke yamaha dirt bike.

    I'm sure you guys are laughing your a_ _ _ _ off at me right now but please hlep diagnose this for me. Is it just a cylinder head, upper or lower bearings (if these things have them)?

    When your done laughing, let me know what you think.

    Thanks


  2. #2
    ph2ocraft's Avatar
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    If you remove the spark plug and look inside you will be seeing the top of the piston.
    Grab screwdriver and use with care.
    Remove the shield on the driveshaft so you can rotate the engine by hand.
    Rotate the engine until one of the pistons come to the top and you can touch it with the scewdriver, you should be able to rotate the engine and watch the stick rise and lower as you rotate the drive shaft back and forth.
    Does this happen with all cylinders or does the screwdriver just fall through one of the piston tops?
    I'm just trying to determine if you holed one of your pistons.

  3. #3

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    I definately have a hole in the 3rd(if 1 is towards the bow) it's the rear piston. I do not need to rotate manually as you suggest. I can see the hole and have already stuck a screwdriver in it. I rotated it by hitting the starter to bring it up top.

    The hole appears to be perfectly round but is left of center.

  4. #4
    Jug Inspector
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    Of all the 750 engine's I've seen burn down it's always been the PTO (the one you're describing)... and I always thought it was supposed to be the MAG since it's farthest from the fuel pump when in stock form. I've always replaced the jug/piston/head etc and ran with it. After tearing the whole engine down of course to check bearings, clean cases, new gaskets and seals, etc. You could get it back up and running for around $300 if your bearings/rods are good and it's just the one cyl. If you do the work yourself. It can be done in a few days.

    Bryan

  5. #5
    Jug Inspector
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    Also, just fixing it is like putting air into a tire that has a hole. It's just going to happen again unless you find the cause; be it clogged carbs, weak fuel pump, leaking gaskets or seals, or an air leak in general.

    OH and don't run the BPR7ES plugs, too hot for today's fuel. Run BPR8ES.

    Bryan

  6. #6
    ph2ocraft's Avatar
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    Bryan, you're forgetting one thing about the pressure within the system.
    The fuel enters and goes past the PTO, Cen and Mag cylinders, it then wants to get returned to the tank.
    With the restrictor in place the pressure starts to build, the first carb to start building pressure is the MAG then Cen and of course the last to get fuel pressure is the PTO.
    Now couple that with a very weak pump pressure, restricted line, plugged switch and it barely gets enough fuel to open the needle and seat at the PTO carb.

    Look at it like this, get a 2 liter bottle and poke 3 hole in in top, center and bottom, start filling it (fuel pump) and what gets pressure first? The top (PTO)or the bottom (MAG)? Not the top (PTO), where the water is entering but the bottom (MAG) where the restriction or end is. As the bottle fills the top (PTO) hole finally starts pushing the water out.
    So the one nearest the top doesn't get the pressure first but last.
    Hope I explained it clearly.

  7. #7

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    could the towing after running out of fuel contributed to this. If water did get into it, would it cause this or is it the million other possibilities. I ask because the point seems to be very valid that if I fix it and don't know the cause, I am simply asking to do the job again.

    This may not be relevant but I think it has non stock carbs because there are what look like air filters above them that say Vilkers or V something racing.

    I really do appreciate all the input.

  8. #8
    Jug Inspector
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    PH I kinda figured that's what it was, but waited for someone else to chime in.

    Running out of fuel on a 2 stroke really isn't the best for them.

    I'm kind of lost, I don't have all the info from a previous post. Is the ski new to you? Did it run fine for a while before this?

    And I just thought of a few more things. From the guy with infinite wisdom: "Check/replace your fuel lines, ALL OF THEM, they get weak and kink over. Also check your fuel selector they tend to start leaking air"

    Although you don't know the reason you can just do what I do. Clean, repair, fix, seal, inspect, and replace everything. Such as pullling the crank seals out and seeing how loose they are, or pulling a jug off and noticing a missing gasket piece. Use all new gaskets and seals, make sure there's no cracks in anything, clean the carbs, make sure jetting is correct, replace all fuel lines, rebuild the fuel pump, and you should be set.

    Bryan

    Bryan

  9. #9
    ph2ocraft's Avatar
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    How about a photo?

    Replace all the lines, replace the fuel knob, replace the pump and then once you're rebuilt be sure to check the plugs/piston wash and get her dialed in.
    I'd use the stock 780 high volume triple outlet pump or the triple outlet kit.


  10. #10
    Connecticut CrazyA's Avatar
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    I'm going to jump in here late in the game, but I've reread your other thread and this one too, and a few things jump out at me. I'm only mentioning these because it seems as though it's so hard to get the whole story on the "net" sometimes.

    It seems as though when the boat originally ran out of gas, you weren't there, your buddy was using your boat. Is this correct?

    You mention the boat being towed and no previsions being made for that.

    Floating red ring in your water seperator.

    Boat was listing from side to side the last time you tried putting it back on the trailer from the water.

    IF you were not there when this entire series of events started, (you can verify this or not) is it possible that whoever was using your machine was out thrashing it and having a good old time rolling it over and submarining it and such?

    It's just that with the floating ring, boat listing, being towed.... lots of water stuff going on, and here's where I'm going with this:

    Maybe while out having a good time, water was injested. And maybe it was hydrolocked before they were done riding and then they continued to ride it with an out of index crank resulting in your holed piston, before "running out of gas". Just so you know, you CAN knock a crank out of index with just the starter button, and then have it start and run, just like someone said in one of your other posts. It doesn't have to be running.... the start button can do it. It seems as though you have all the makings and symptoms of an out of index crank. I'm NOT saying that it IS, but it very well MAY be.

    When you got your machine back, was the seat any heavier than normal? I ask because sometimes people will say,

    A) "I don't know what happened, I was just riding it and it quit"

    B) "Did you roll it over and take on water?"

    A) "No"

    B) "Well, how come your seat is waterlogged and weighs an extra 10 pounds?"

    A) "Well, maybe just a few rollovers"

    B) "Um, sure, OK"


    .

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