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Thread: 250SX Piston - Any Guesses what caused this?

  1. #1
    Join Date
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    250SX Piston - Any Guesses what caused this?

    Any guess what caused this? I thought excessive piston to cylinder clearance causing the piston to "rock" and skirt damage, but noticed the piece gone seems to match the rod quite well. Maybe pure coincidence?
    Rod bearing and wrist pin both tight. Motor was running before disassembly.
    Piston skirt is scuffed bad both sides, I think dirt ingestion may have played a factor. Had only a metal screen air filter when I got it, and I figure it probably sucked a lot of dust.

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    1985 250sx
    1982 ATC185s
    1984 200es

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  2. #2
    BarnBoy is offline Just Too Addicted Arm chair racerJust too addicted
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    Yikes, yeah I would say it sucked in a little dirt. I would guess that broken piece would be from piston slap.

    Why did you pull it apart? Low compression? Obviously it needed to be taken apart but I am just wondering.
    1984 HONDA ATC200M - OG, mid-restoration
    1981 HONDA ATC200 - future build
    1981 HONDA ATC185S - parts
    1984 ATC200X - roller, future build
    1984 Honda ATC250r - in a million pieces- ISO grab bar, PM if you have one

    Da velder
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  3. #3
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    Quote Originally Posted by BarnBoy View Post
    Yikes, yeah I would say it sucked in a little dirt. I would guess that broken piece would be from piston slap.

    Why did you pull it apart? Low compression? Obviously it needed to be taken apart but I am just wondering.
    Smoked, and sounded bad, I thought horrible timing chain and guides, but I'm thinking now it was mostly piston slap.


    Sent from my SM-G903W using Tapatalk
    Rides:
    1985 250sx
    1982 ATC185s
    1984 200es

    Always Hoping For a Maritime Trikefest- http://www.3wheelerworld.com/showthr...s-where-you-at

    "Wear Limits Are Just A Suggestion"

  4. #4
    BarnBoy is offline Just Too Addicted Arm chair racerJust too addicted
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    Oh, ok. Yeah, I think you are right. How does the cylinder look? I would assume there is a good chance it needs to be bored over based on the looks of that piston.....did you measure it yet?
    1984 HONDA ATC200M - OG, mid-restoration
    1981 HONDA ATC200 - future build
    1981 HONDA ATC185S - parts
    1984 ATC200X - roller, future build
    1984 Honda ATC250r - in a million pieces- ISO grab bar, PM if you have one

    Da velder
    _______________________________________________
    Feedback:
    http://www.3wheelerworld.com/showthr...ck-for-Barnboy

  5. #5
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    I've already got a .020 oversized piston waiting haha. I was expecting to bore over anyway, I pulled the head a few weeks ago to look at the piston for an oversized stamp and measured the cylinder. Still standard bore.

    Sent from my SM-G903W using Tapatalk
    Rides:
    1985 250sx
    1982 ATC185s
    1984 200es

    Always Hoping For a Maritime Trikefest- http://www.3wheelerworld.com/showthr...s-where-you-at

    "Wear Limits Are Just A Suggestion"

  6. #6
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    see if there is aluminum from the piston in your cylinder.


    PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR

  7. #7
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    Looks to be a small amount of metal transfer near the bottom. Definitely seen a lot worse on snowmobile cylinders... I'm a Polaris tech by day haha

    Sent from my SM-G903W using Tapatalk
    Rides:
    1985 250sx
    1982 ATC185s
    1984 200es

    Always Hoping For a Maritime Trikefest- http://www.3wheelerworld.com/showthr...s-where-you-at

    "Wear Limits Are Just A Suggestion"

  8. #8
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Quote Originally Posted by Gearheadtom View Post
    Looks to be a small amount of metal transfer near the bottom. Definitely seen a lot worse on snowmobile cylinders... I'm a Polaris tech by day haha
    can you post a photo of the end of the spark plug?

    at least part of the cause of the damage is that it seized.

    it is impossible for it to be so loose that the rod hit the piston.

    i would just bore it out and remove the clutch cover and clean the oil filter and look for sand and metal in the oil . drag a magnet thru the oil to see what you get . maybe run some new oil in there just for around 30 minutes then drain it to try and rinse any more debris out that might be in there.
    check the rocker arms and cam and cam bore in the head etc.

    use good oil like mobil 1 v twin 20w-50


    PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR

  9. #9
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    Motor had many gasket leaks, so it was getting a complete tear down anyway. Cam and rockers looks good, very little wear.

    Sent from my SM-G903W using Tapatalk
    Rides:
    1985 250sx
    1982 ATC185s
    1984 200es

    Always Hoping For a Maritime Trikefest- http://www.3wheelerworld.com/showthr...s-where-you-at

    "Wear Limits Are Just A Suggestion"

  10. #10
    BarnBoy is offline Just Too Addicted Arm chair racerJust too addicted
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    How does the rod bearing feel? Any play?
    1984 HONDA ATC200M - OG, mid-restoration
    1981 HONDA ATC200 - future build
    1981 HONDA ATC185S - parts
    1984 ATC200X - roller, future build
    1984 Honda ATC250r - in a million pieces- ISO grab bar, PM if you have one

    Da velder
    _______________________________________________
    Feedback:
    http://www.3wheelerworld.com/showthr...ck-for-Barnboy

  11. #11
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    No play in the rod at all.

    Sent from my SM-G903W using Tapatalk
    Rides:
    1985 250sx
    1982 ATC185s
    1984 200es

    Always Hoping For a Maritime Trikefest- http://www.3wheelerworld.com/showthr...s-where-you-at

    "Wear Limits Are Just A Suggestion"

  12. #12
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Quote Originally Posted by Gearheadtom View Post
    No play in the rod at all.
    Damn, I wish I could still say that.



    PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR

  13. #13
    Join Date
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    I'm thinking that part of the cause was a wrist pin that began to seize. There's galling on the wrist pin. I've seen similar but worse damage on engines with completely seized wrist pins.
    So I might have to send the crank away to have the rod replaced, not a shop in the city does it.

    Last edited by Gearheadtom; 06-24-2017 at 02:34 PM.
    Rides:
    1985 250sx
    1982 ATC185s
    1984 200es

    Always Hoping For a Maritime Trikefest- http://www.3wheelerworld.com/showthr...s-where-you-at

    "Wear Limits Are Just A Suggestion"

  14. #14
    Join Date
    Oct 2008
    Location
    NB, Canada
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    852
    Rod kit is ordered, and sending my crank away once I get it. CV Tech in Quebec, Canada is who I'm sending it to. We deal with them a lot at work with all the Polaris stuff and no issues.

    Started stripping the bottom end, and found that piece that always breaks for the shifting (can't remember the proper name), has been "repaired" before. Looks like a bolt was cut down, and a nut was held in place with a little JB Weld haha.


    Sent from my SM-G903W using Tapatalk
    Rides:
    1985 250sx
    1982 ATC185s
    1984 200es

    Always Hoping For a Maritime Trikefest- http://www.3wheelerworld.com/showthr...s-where-you-at

    "Wear Limits Are Just A Suggestion"

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