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  1. #1

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    Starts and idles good. Squeeze throttle and lugs, runs but won't go over 5mph

    Checked compression. 120 and 130. Has spark. Just won't turn up any RPM's. This is an 800 power valve motor. Suggestions?


  2. #2
    check all fuel lines, carbs need rebuild, basically anything fuel related is where I would start first

  3. #3
    Had this on my 1200 NPV last week too. Not enough info to really diagnose but if you already rebuilt the carbs, try adjusting the high speed needles. I was too rich with stock settings. Turned them back about 1/8 turn each and it jumped out of the hole...till it broke 4 miles later anyway (front rod bearing was shot).

  4. #4

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    Pulled plugs and noticed one still looked brand new with A virtually all white insulator and the other dark grey/black. Need to check fuel lines I guess next.

  5. #5
    did you test it out of water? that could be important

  6. #6

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    Quote Originally Posted by Extrnoa View Post
    did you test it out of water? that could be important
    Was running like that in the water. Haven't done much with it since. Looking for some direction before I do something that involves parts and money. Want suggestions on where to start. I have my own thoughts but want some others to pass on thoughts and suggestions.

    Thanks

  7. #7
    Echo's Avatar
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    Quote Originally Posted by Jace View Post
    check all fuel lines, carbs need rebuild, basically anything fuel related is where I would start first
    ^^^^^^^ This is the only right thought and suggestion as to where to start. I would also drain, clean the tank, and replace filter.^^^^^^^

    However i will give you a couple redundant thoughts and suggestions you so disire if it will motivate you to get that beast running right and on the water.

    First off as already mentioned, With the limited history given in this thread all you have done is check compression and spark on what might be, a new to you ski, or been stored for awhile or maybe you been riding 7 days a week 10 hours a day and this just occured spontaneously this morning.........( I could guess all night, or at least until I have reached maxium alcohol intake, not far from it now.)

    Any carberated 2 stroke pwc engine that has been setting for a long duration, or that you recently took ownership of needs a complete fuel system overhaul. This is the only way to insure proper fuel delivery other than reading piston wash for fine tuning.


    Carberated 2stroke basics in a nutshell: A mixture of Air/Gas gets sucked into that hunk of metal under the seat where it is subjected to Compression. Once pressureized to a minium needed psi a high intensity Spark is enterduced creating an explosion that that is transfered into centrifical force thus causeing rotation of the crank shaft.
    The three bold items up there are listed in order of introduction however all are equally important. If any one of them are out of spec things get wacky. There are no mysterous puzzles here. You need all three. Could be an air leak but unlikely and is the last thing you want anyway.

    The fuel system is fairly cheap to overhaul. Less than $100 If you are capible of doing it yourself.

    How much money and time is that blown engine going to cost ya cause you dumped gas into it, and hoped for the best? Even if it does run great, mine did, and the plugs are reading good, mine did. There is a strong probabilty that the screens or restricted from corrosion due to eythenol and setting for just under a year, mine were. And this restriction might lead to creased/damaged diaphrams and check valves, mine did. And those couple of weekends of carefree hoping for the best could cost you more than the ski is worth, mine woulda, (cept i am capable and own the proper tools to do most of my own work.)

    My last suggestion(s) would be, when you ask for advise on a public forum with an undisputed reputation of having a very knowledgeable group of guys that have not only pushed these things to the limit and beyond.(Many of them do this full time for a living all over the industry, from sales all the way to the point of engineering either new or exsisting parts.)Would be to listen and accept the help or ideas that you came asking You are not going to get alot of replies when you have already been given the proper advise. Especially on the old two strokes where a quick search will provide a book of pages with hours of reading the same suggestion(s) over and over.
    Last edited by Echo; 10-08-2014 at 01:50 AM.


  8. #8

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    A difference of 10 psig between the two cylinders suggest a trashed piston.... especially when one plug is clean and the other is dirty. Do you suspect the dirty plug that is grey may be aluminum.... some folks would say that the plug looks "muddy". Is that what it looks like to you?

    If so, you probably need to pull the head and inspect. Myself, I would get a small "bend-a-light" and stick it into the spark plug hole with the piston completely down. While in a completely dark garage, I would look into the cylinder toward the exhaust port side to verify any gauging on the cylinder wall.

  9. #9
    Myself's Avatar
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    First thing I would do is pull plugs and ohm them out. I can't count the new plugs bad or going bad without much run time lately, quality control in non-existent. Sounds to me like the clean plug is shorted directly to ground and therefore not firing inside the cylinder.

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  11. #10
    Echo's Avatar
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    Quote Originally Posted by salty View Post
    A difference of 10 psig between the two cylinders suggest a trashed piston.... especially when one plug is clean and the other is dirty. Do you suspect the dirty plug that is grey may be aluminum.... some folks would say that the plug looks "muddy". Is that what it looks like to you?

    If so, you probably need to pull the head and inspect. Myself, I would get a small "bend-a-light" and stick it into the spark plug hole with the piston completely down. While in a completely dark garage, I would look into the cylinder toward the exhaust port side to verify any gauging on the cylinder wall.
    120 compression is by no means a trashed piston yet. 90-105 is where you start seeing decent damage, or noticable wearing. 10% difference is considered safe, and he is well within that. We don't even know if the lower compression is the one with bad plug. Looking in with a light is a good idea. It is hard to see with the angle involved, so if you are able to make out any scoring at all it is a good chance it is relevant.

    This is why we need a more detailed description and history.

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