Piston Dropped at 5700 km
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  1. #1
    Senior Member Drapes's Avatar
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    so the shop just called, apparently that "clunk" was my piston dropping... tappets are fine. he said "you mustve been going too fast/revved it too high.



    how does this happen on a bike that is jetted low?

    why did this happen at 5700 km?



    should i go for the top end rebuild now, as im sure to put another few thousand on it this summer..



    1989 Tw200
    1991 Tw200
    2008 WR250R
    2004 Ford Ranger FXR Lvl II

  2. #2
    Senior Member elime's Avatar
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    What do you mean "piston dropping"? Did it break or did you burn a hole in it? If you burned or melted a hole in the piston you are running it to lean. If it were me I would just put a new piston in it and richen the mixture a little (if in deed it is running to lean).
    Long live the internal combustion engine!

  3. #3
    Senior Member Drapes's Avatar
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    Quote Originally Posted by Tony View Post
    What do you mean "piston dropping"? Did it break or did you burn a hole in it? If you burned or melted a hole in the piston you are running it to lean. If it were me I would just put a new piston in it and richen the mixture a little (if in deed it is running to lean).


    not sure exactly how to explain it, the tappets were fine- the intake valve dropped? you could see the bottom of something through the spark plug hole. Im not a mechanic, perhaps i misunderstood the fellows at the shop.



    the valves would not stay adjusted prior to the failure
    1989 Tw200
    1991 Tw200
    2008 WR250R
    2004 Ford Ranger FXR Lvl II

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  5. #4
    Senior Member Stromper's Avatar
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    Broken valve spring ?

  6. #5
    Senior Member pgilles's Avatar
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    If he used the adjective "dropped" he was probably saying a dropped valve.



    Broken valve spring like Stomper said. Valve retainer let go. Camchain and/or tensioner failed causing piston-to-valve contact. Broken valve stem.



    See if you can get some pictures. Haven't heard of much of this one from the TW's. It's a rarity from what I've gathered cruising this forum for a few years



    Not sure what warranty is still available, if any, being a 2010 but might be worth checking.
    Sold bike.



    Youtube vids of old TW's acceleration:

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  7. #6
    Senior Member atleastbehandy's Avatar
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    My 2005 "dropped" a valve. I was getting valve float at high RPM due to overly tight valve clearances (the stems were mushroomed). Tried to back-off the adjusters but both were cracked.



    Piston finally hit the intake valve about a block from home.



    So I bought a complete used head from a 2006 off ebay for $270 - replaced the head in the back-yard - few hours later I was riding again!
    2005 TW200, 2" PowerMadd bar riser, Tusk D-Flex Hand Guards, PowerMadd Hand Muffs, Kick-Start, Valco Cup Holder, Givi E45N Top Case, Inline fuel filter, Storage Tube with MSR bottle, 45 Tooth sprocket, Stebel Low Tone horn, #130 Main Jet / no needle shims / 1.5 turns out on idle, Jimbo Shield, DID O-Ring chain, Clarke XT250 4.1 Gal tank, Custom Cycleracks

  8. #7
    Senior Member frog13's Avatar
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    "Valve float"???.......could you educate me please?.

  9. #8
    Junior Member kmxman's Avatar
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    Valve float is a term used to describe when the intake and exhaust valves do not return to their seat in at the time they are suppose to as dictated by the profile of the cam. In essence the valves are staying open all the time. This is usually caused by high rpm or as previously mentioned to tight of valve clearance. Cheers!

  10. #9
    Senior Member Ayers Garage's Avatar
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    ...or weak valve springs.

  11. #10
    Senior Member frog13's Avatar
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    Thanks for the info!.

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