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  1. #1

    2007 NPV CYL 2 Meltdown, whats the problem?

    Well Here is the story to go with the tear-down.

    I was riding on the lake for about 7-8 mins when my boat just suddenly bogged down, made a funny noise from the engine , pinging on metal sound-ish and i shut her down. I pulled the seat to look for problems and nothing visible was wrong, all oil lines were on for instance.

    I pulled the plugs, number 2 Cyl had metal on the plug i could see and i knew i had major problems. Tried to start, but wouldn't turn over, she was seized up!

    Pulled the boat in the shop, pulled the head and sure enough number 2 was toast, metal bits on top of the piston, Cleaned them off as the piston was just down from the top and pulled exhaust to see if i could get the jug off. She was stuck in the good but i eventually got the jug off, its got 3 deep scratches and needs to be replaced. piston top is melted but rings are in place. The cyl head was oily underneath as well.

    The first things i noticed when i unbolted the jug was there was massive slop in the rod. This was not good, So crank is probly cooked too, rod bearing is totally done rod has lost its tempering bu the look of the metal. Crank moves easy now the jug is off, but there was metal bits all in the bottom of the case.

    I got quite a bit out some large bits, mostly flat. but motor has to come out now to clean it out a check out the beating marks on the inside bottom of the case.

    The oil pump is hooked up and lines and cable, so i will get pics tomorrow (did after work and didnt have my camera). Piston 1+3 look great, The was the 2nd time out this year, I had fresh 91 in it with the extra oz oil per gallon. Fuses good too. I forget what my settings of the EFI controller are atm but i will check tomorrow.

    Still not sure what happened, Ideas? Reed? Fuel inj quit? No codes on the display or bells or anything when it happened either.

    Help?

    Pics:

    Head:



    Cyl 1:


    Cyl 3:


    Cyl 2:







    Jug 2:


    Case:
    Last edited by zakre; 06-21-2011 at 06:10 PM. Reason: added pics


  2. #2
    PolarisNut's Avatar
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    Need pics of the piston to have an idea what may have happened.

  3. #3
    Bump for pics !

  4. #4
    PolarisNut's Avatar
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    Looks like the rod bearing came apart and shot debris through the motor. That's what appears to have damaged the piston. Is the oil line still on the middle carb? Crank looks dry to me.

  5. #5

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    Polaris,
    Not to contradict but debris looked to be on top of piston. If rod bearing gave out would metal work by both rings to bounce around under head?
    I'm only on my second rebuild so you've seen much more than I but I like to get an understanding of these engine failures and I can't quite get my arms around this one.

  6. #6
    Yes all oil lines are on as i said above, I am starting to think it mihgt have been the rod bearing go then went from there, the head has a film of oil on the second piston so it must have been getting oil. THere was debris on top of the piston, but much more in the bottom of the block and some in the exhaust port as well, this is a EFI ski not carb. I am still goin to check the reeds soon as i take it out.

  7. #7
    crashhard's Avatar
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    It looks like the plugs were pretty new, any chance the middle one was not tight? Dont know if you remeber when removing. But I had a friend loose his motor being too scared to overtighten his plugs.

    Just saw second time out, how long were both times?

  8. #8
    Superman! fivespeedsteed's Avatar
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    if the rod bearing on the big end goes, wont that allow the piston to wallow around in the jug and chew up the sides like that? i can see the metal shavings on the big end rod bearing.

  9. #9
    PolarisNut's Avatar
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    Quote Originally Posted by toyterrific View Post
    Polaris,
    Not to contradict but debris looked to be on top of piston. If rod bearing gave out would metal work by both rings to bounce around under head?
    I'm only on my second rebuild so you've seen much more than I but I like to get an understanding of these engine failures and I can't quite get my arms around this one.
    The debris comes up the transfer ports with the air and fuel...it could never pass by the rings. Not an uncommon failure with a 2 stroke

  10. #10

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    The debris comes up the transfer ports with the air and fuel...it could never pass by the rings. Not an uncommon failure with a 2 stroke
    Gotcha.

    Thanks

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