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Big Bore KitsBig Bore Kits

Big Bore Kits from Rocky Mountain ATV/MC

High quality off road big bore kits.

Latest Dirt Bike Big Bore Kits Reviews – You could win up to $500 for reviewing products!

  • Cylinder Works Big Bore Cylinder Kit

    Cylinder Works Big Bore Cylinder Kit

    MARTIN in CA

    The vertex piston oil ring was pretty cheesy

    Not to sure how long this thing will last . Over all every thing was allright but the oil ring was pretty cheap . You would think they would give a better oil ring thats the only thing i could see going wrong .the stock pistons oil ring was 3 times stronger. Will let u know how it holds up thanks

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  • Yamaha GYTR Ported Cylinder Head Assembly

    Yamaha GYTR Ported Cylinder Head Assembly

    James in TX

    GYTR Head

    Expensive engine mod but if you are serious about powering up your YZ grab this and get to the front. Need to use VP u4.4 but you should already be using that if your racing at all . Be sure to set the new mapping to the ECU !

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  • Dubach Racing Engine Relocation Kit

    Dubach Racing Engine Relocation Kit

    cody in MO


    Put this on my bike along with the Dr. D radiator lowering kit and the two together made my bike handling a lot better than it ever did before. Recommend both kits for anyone with a 10-13 yz450

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  • Wiseco Big Bore 440 Kit

    Wiseco Big Bore 440 Kit

    TROY in CA

    Best mod ever

    This was buy far the best upgrade I did to this quad. Great fit.

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  • Athena Big Bore Kit

    Athena Big Bore Kit

    DAVID in CA

    Athena 290 big bore wr/yz

    I have ran this big bore for three years and have great success with it, makes great bottom end and mid range power. I have ran it on my 08 yz250f with a wr trans and rekluse clutch and hot cams, awesome woods bike.

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