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HOME » 109 Monster Big Bore Kit

Revolution Performance 109" Monster Big Bore Kit

(Fits 1984-1999 80" EVO style motorcycles with 4.625" stroke crankshaft)


The Revolution Performance 109" EVO Monster Big Bore Kit is the key component to build a devastating 109" 1984-1999 EVO engine. The monster 109" kit comes with our state of the art all aluminum NSC plated cylinders which last longer and run cooler than the OEM cylinders. The cylinders are matched with a premium forged piston kit and a Cometic head and base gasket kit.

    109" Monster Big Bore Kit comes with:

  • NEW 3.875" all aluminum Nickel Silicon Carbide (NSC) plated cylinders in your choice of finish: All Black, Black Highlighted or Natural
  • 10.5:1 compression ratio flat-top piston kit
  • Cometic head and base gasket kit (.030 head gasket / .020 base gasket)
  • The 109" Monster Big Bore Kit requires additional engine modifications to install and benefit from our other products and services.

    Required Services:

  • Case bore service
  • Crank balance service
  • Recommended Services:

  • 109" Monster CNC Cylinder Head Porting Package

    ***NOTE: Compression ratio is dependent on the cylinder heads combustion chamber volume***

    ***NOTE: Dyno chart represents 109" Bolt-On Big Bore Kit, Velocity CNC ported heads, T-Man .625 cams, Mikuni carb, Bassani 2-into-1 exhaust***

For questions on our big bore kits, please contact our sales technicians directly at: 1-866-892-2109 M-F 8:30 A.M. - 5:00 P.M. CST.

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