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Thread: What piston size would i need for a 65.72 bore?

  1. 10-02-2016, 07:21 PM #1
    niftylittleguy
    niftylittleguy is offline First Time Rider Arm chair racerNew to the board
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    What piston size would i need for a 65.72 bore?

    I picked up a 1984 200x and the bike had a loud piston knock noise and it smoked a lot. When i opened up the top end I found that the piston was 64.5mm and the bore of the cylinder was 65.72 or so. The piston is a brand new wiseco. Would a new piston that is 65.5mm work in that 65.72 bore?
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  2. 10-02-2016, 09:19 PM #2
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    arlaunch
    arlaunch is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    I like to send jugs away to professionals who bore the cylinder to match the exact piston that they supply.

    Pistons can measure differently in different locations due to the anticipated exhaust side being hotter blah blah blah

    How this particular situation exists in real life is shocking to me.

    What else did the previous owner fix?

    1984 Honda Big Red ATC 200ES (Emma)
    1985 Honda 200X ATC (Pretty Boy)
    1985 Honda 250R ATC (Dr. Fast)
    1985 Honda 250R ATC ( 77 )
    1985 Honda 250R ATC (Baller)
    1986 Honda 350X ATC (Go Go Girl)

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  3. 10-02-2016, 09:24 PM #3
    DohcBikes
    DohcBikes is offline Trikein' Away Lord of the trike
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    That's peculiar since a stock piston is 65mm. This is why we can't have nice things.
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  4. 10-02-2016, 09:40 PM #4
    niftylittleguy
    niftylittleguy is offline First Time Rider Arm chair racerNew to the board
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    I hope nothing else is wrong with the engine. Im looking to get rid of this bike once im done putting it back together. So im thinking of picking up a 65.5mm piston and throwing it in.
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  5. 10-02-2016, 09:44 PM #5
    DohcBikes
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    Quote Originally Posted by niftylittleguy View Post
    im thinking of picking up a 65.5mm piston and throwing it in.
    If you stand far enough back, and get a video of it, maybe dudeperfect will make you youtube famous.
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  6. 10-02-2016, 09:47 PM #6
    niftylittleguy
    niftylittleguy is offline First Time Rider Arm chair racerNew to the board
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    Well i'll have .2mm of play so i think i might make the shot. LoL
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  7. 10-02-2016, 09:53 PM #7
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    El Camexican
    El Camexican is offline Power User Catch me if you can
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    What did you use to measure the bore?
    It sucks to get old
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  8. 10-02-2016, 10:34 PM #8
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    arlaunch
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    Quote Originally Posted by niftylittleguy View Post
    I hope nothing else is wrong with the engine. Im looking to get rid of this bike once im done putting it back together. So im thinking of picking up a 65.5mm piston and throwing it in.
    I strongly advise against that option.

    Remember at the very minimum you need to get the bore honed to set the new rings.

    Let the pro's bore it with the correct forged or cast piston clearance.

    Do everything else correctly and survive with a good running, reliable engine.

    1984 Honda Big Red ATC 200ES (Emma)
    1985 Honda 200X ATC (Pretty Boy)
    1985 Honda 250R ATC (Dr. Fast)
    1985 Honda 250R ATC ( 77 )
    1985 Honda 250R ATC (Baller)
    1986 Honda 350X ATC (Go Go Girl)

    Feed Back: http://www.3wheelerworld.com/showthr...k-for-arlaunch
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  9. 10-02-2016, 10:39 PM #9
    niftylittleguy
    niftylittleguy is offline First Time Rider Arm chair racerNew to the board
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    Quote Originally Posted by arlaunch View Post
    I strongly advise against that option.

    Remember at the very minimum you need to get the bore honed to set the new rings.

    Let the pro's bore it with the correct forged or cast piston clearance.

    Do everything else correctly and survive with a good running, reliable engine.
    The cylinder has been honed previously. I dont think it needs to be honed again.
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  10. 10-02-2016, 10:40 PM #10
    niftylittleguy
    niftylittleguy is offline First Time Rider Arm chair racerNew to the board
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    Micrometer i got off amazon.
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  11. 10-02-2016, 10:53 PM #11
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    tripledog
    tripledog is offline I could be geriatricdog... at my age Got the holeshot
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    This looks like a job for loganm, AKA "the piston whisperer".
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  12. 10-02-2016, 11:06 PM #12
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    John Tice
    John Tice is offline At The Back Of The Pack Arm chair racerFirst time rider
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    Howdy mate; your numbers are going all over the place
    64.5mm = 2.53937”
    65.5mm = 2.5787”
    65.72mm = 2.5874”
    A Wiesco piston for a 65mm bore would be .002”. Too many decimal points to work with, you’ll turn your brain in knots trying to work the numbers.
    A 65.72mm piston fits a 65.75mm bore, the difference .03mm is the new skirt clearance, .00118” don’t believe it. This is why the skirt clearance is printed on the Box; mostly, Wiesco pistons increase in 1/2mm or .020” steps.


    John Tice
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  13. 10-02-2016, 11:07 PM #13
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    El Camexican
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    Quote Originally Posted by tripledog View Post
    This looks like a job for loganm, AKA "the piston whisperer".
    LOL!!! Hell yea!!! He'd get a 66mm piston in that hole faster than you can scream "Put down that !"
    It sucks to get old
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  14. 10-02-2016, 11:28 PM #14
    tripledog's Avatar
    tripledog
    tripledog is offline I could be geriatricdog... at my age Got the holeshot
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    Quote Originally Posted by El Camexican View Post
    LOL!!! Hell yea!!! He'd get a 66mm piston in that hole faster than you can scream "Put down that !"
    Why must you leak down upon people that ask questions but don't listen to answers?
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  15. 10-03-2016, 12:20 AM #15
    niftylittleguy
    niftylittleguy is offline First Time Rider Arm chair racerNew to the board
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    The bore i have is 65.72mm. The closest piston to the bore i can get is 65.5mm. So there would be a .22mm difference.
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