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Info ZXR250a oversize pistons

Discussion in 'Kawasaki 250cc In-line 4's' started by stevodude, Dec 3, 2017.

  1. stevodude

    stevodude Active Member Premium Member Contributing Member

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    HI,

    the zxr250a has 48mm bore 34.5 stroke.
    I picked up a zx2r a while back, but i am now stripping it back and rebuilding.

    all bores are 48.20xmm so from standard 48mm bore I need a first oversize piston and rings which is 48.25

    found a few standard ring sets for 48mm, and further searching returns NO zxr250 48.25mm pistons.

    But there are quite a few fzr250rr os piston and ring sets 48.25mm, I am wondering if the pistons are similar, as the images on aliexpress for the fzr look VERY similar to the zxr250.

    The other option is to bore it out to 49mm and fit std bore zxr250c pistons.

    Looking difficult, but not impossible to rebuild...
     
  2. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club

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    Going to 49mm would be your best bet, if the liners have enough meat left on them.
     
  3. Andych

    Andych Well-Known Member Premium Member Contributing Member

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    You would also need to ensure crown height, wrist pin diameter, ring height, any wrist pin offset etc were all exactly the same... my bet is they wont be... but you never know your luck... If it were me I would do an awful lot of investigation before laying out $ for a rebore and new pistons and rings.
     
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  4. ShaneP

    ShaneP Well-Known Member Premium Member Contributing Member

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    @GreyImport did I see a comment on Facebook in the zxr group about this very topic, with your 'name' on it?
     
  5. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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  6. ShaneP

    ShaneP Well-Known Member Premium Member Contributing Member

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    Screenshot_20171207-074200.png
    Might be an avenue to try.
     
  7. Mr_Muddle

    Mr_Muddle Active Member

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    Yeah that was me.

    The problem with oem 49mm pistons is that the gudgeon pin is really low on the piston so you have to beef it way up using barrel gaskets to avoid valve strike. I have been running this for a few years now and I hate it. So I have spent some toime and got oversize and standard ones sorted from germany.

    The price is reasonable. new piston and rings will set you back $110 for oem 49mm and pins and circlips say an extra $10-$20. These are being custom made on limited run by wossner in germany so the quality will be there.
     
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