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  1. #1

    GP1800 engine tear down piston replacement

    hello,
    so i just bought my gp1800 last year, its a 2018 and i idiotically ignored the oil level after
    changing it at 25hrs. i went to flush it after a ride and it wouldnt start back up. this is at
    only 60hrs and i was told id be good until 100hrs, so low oil wasnt even on my mind.
    this is my first ski and i didnt know much at the time, so i kept trying to start it until
    i realized it probably was the low oil sensor so i took it home to give it more oil and
    nothing even came out when i went to pump out excess oil.

    So i refilled the oil 10w 40 yamalube and ran it for 10 more hours and noticed oil
    was leaking out of my engine breather and once i hit 72hrs my oil was back to empty.
    i took it home and checked the compression and it was 80s to 90s. i decided to open up
    the engine and get the pistons out and sure enough they were scratched up at the top
    as well as cylinders 2 and 3 only at the very top though. i have pictures ill post them
    but my question finally... how should i repair these cylinders? i have a hone and a ball hone
    and a ridge reamer and im getting new pistons and rings. what do u guys think?









    UPDATE****

    so i just honed the cylinders and they came out pretty well, it wasnt scratched just had aluminum from
    the stock pistons melted to the surface. im pretty sure i didnt take off much at all, hoping i can order the
    same size pistons from riva and not have a problem 86mm.... otherwise im just gonna take it to a machinist
    and have it lined up for 87mm pistons cause i really dont ever want to open this up again lol

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    Last edited by marksamm; 05-12-2019 at 12:07 AM.


  2. #2
    Hurricane1000's Avatar
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  3. #3
    Hurricane1000's Avatar
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    Quote Originally Posted by Hurricane1000 View Post
    ?
    Will the cylinders get by with a light hone job?

  4. #4
    that is the question i came here for

  5. #5

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    if it doesnt get cleaned up you'll be taking it apart again...

  6. #6
    Looking at your photos, I doubt its going to be as simple as replacing slugs. I thought I remember reading that these motors have sleeves.

    I’m sure experts will offer more help and good luck. What did the bearings and cam journals look like? Unusual that pistons would seize before bearings.

  7. #7
    It didnt seize just wasnt starting when oil was low, i was just getting bad blow by and low compressions.. plus the leaking oil from the breather tube but yea everything else internally looked fine brand new

  8. #8
    Wrong word, I mean lack of lubrication usually will cause damage in other places before you see piston/cylinder wall damage.

    if you feel scratches in cylinder walls, honing isn’t going to work.

  9. #9
    Quote Originally Posted by TurboX View Post
    Looking at your photos, I doubt its going to be as simple as replacing slugs. I thought I remember reading that these motors have sleeves.

    Im sure experts will offer more help and good luck. What did the bearings and cam journals look like? Unusual that pistons would seize before bearings.
    Engines are sleeved, the sleeves are cast into the block on pretty well invisible. You can find them with a magnet.

  10. #10
    Thanks.

    Im shocked that nobody has commented and given the OP more info.

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