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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 Dual Sport Big Bore Kits Reviews – You could win up to $500 for reviewing products!

  • Dubach Racing Engine Relocation Kit

    Dubach Racing Engine Relocation Kit

    KEVIN in UT

    Easy Install

    Smooth instal.Take your time and follow the instructions.Made minor improvemen to the bike handling

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  • Cylinder Works Big Bore Cylinder Kit

    Cylinder Works Big Bore Cylinder Kit

    Taylor in AL

    Awesome kit

    The cylinder works kit is a very reliable upgrade over stock. Comes with everything necessary to install it. There's no replacement for displacement!

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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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  • Wiseco Big Bore 440 Kit

    Wiseco Big Bore 440 Kit

    Jacob in TN

    RMATV customer service and product performance

    Very dissappointed in the knowledge of the RM sales team. They told me that all I would have to do (to my 2004 400ex) was press out the old sleeve and press the new one in, however that was not the case. The machine shop had to press out the old one, bore and counter bore the cylinder in order to press the new sleeve in, then after getting the cylinder back I went to put it all together just to find out that the sleeve had to be bored to the piston also. Wasn't very costly to have done ( about $120) but would've been nice to have known all this from the start. Wisecos 440 big bore kit is the bomb tho, along with hot cams stage 2 cam and a dyno jet jet kit my quad is wicked fast.

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