Choose a vehicle:

User Tip: If you're unsure of your vehicle type, you may skip the machine type selection box.

» Log in to use your Rider Profile Machines

Please select make, model and year

Big Bore KitsBig Bore Kits

Dirt Bike Big Bore Kits

Every rider craves more power from their dirt bike, more torque to pull from. Modifying your top end with an aftermarket big bore kit can be a fairly easy way to deliver the power that you’re after by increasing torque and horsepower to give you noticeable power gains through all ranges.

Aftermarket big bore kits include larger pistons and cylinders which typically increase the engine size by around 3 mm – and it only makes sense that the larger the engine, the more power you’ll get. The cylinders look nearly identical to stock and usually include everything you’ll need, such as:

  • Piston
  • Cylinder
  • Piston rings
  • Wristpin
  • Circlips
  • Top end gaskets

These kits are made for easy installation and include all the parts you will need to completely rebuild your top end. If you’re up to the task of doing the mechanics, we’ve got a part one and part two instructional video series to show you how to replace the top end on your dirt bike. Make sure you have all the tools you’ll need as well as a service manual and we’ll do our best to guide you through the installation.

Leave your competition in the dust or just impress your buddies with your new-found power and performance when you upgrade your top end with a big bore cylinder kit by Cylinder Works from Rocky Mountain ATV/MC today!

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

    Daniel in NJ

    Catastrophic Failure

    Bought this kit, install went great! Installed this and hotcams at same time. Broke in cams and cylinder as per specs. Took out for first ride and changed oil after, FOUND BROKEN WRISTPIN CIRCLIP IN OIL. Called company, they overnighted part without hesitation. Found other half in engine, removed it with magnet. Installed new ones, bike ran like a dream. 2 months in, let clutch out of a turn and the bike died on the spot with a small pop noise. Broke down engine AGAIN and found the wristpin slide out of place due to another failed circlip, the connecting rod threw the piston up into the head bending my valves and bent the connecting rod while scoring my cylinder wall at the same time. 2,000 in damage thank you

    Read All Reviews
  • 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.

    Read All Reviews
  • 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

    Read All Reviews
  • 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.

    Read All Reviews
Frequent Buyer ProgramParts Finder