background graphic
background graphic
Revolution Performance logo and home page link

A subsidiary of

Millennium Technologies Parent Company

HOME » 90 Monster Big Bore Kit

Revolution Performance 90" Monster Big Bore Kit

(Fits 1986-present Sportster, XB and XR1200 style Harley Davidson motorcycles)


The Revolution Performance 90" Sportster, XB and XR1200 Monster Big Bore kit is the key component to build a devastating 90" 1986-present Sportster, XB and XR1200 style engine. The monster 90" 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 available in two different compression ratios and a Cometic head and base gasket kit.

    90" 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
  • Forged 11.4:1 compression ratio flat-top piston kit (-2.8cc)
  • Cometic head and base gasket kit (.027 head gasket / .018 base gasket)
  • The 90" 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:

  • 90" Monster CNC Cylinder Head Porting Package

  • ***NOTE: Compression ratio is calculated using 62cc chamber***

    ***NOTE: Dyno chart represents 90" Monster Big Bore Kit, Velocity CNC ported heads, Redshift .643 cams, 48 mm throttle body, Screamin Eagle heavy breather, TP roller rockers, Screamin Eagle race tuner and Thunderheader***

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.

Millennium Technologies Family of Companies logo Powersports Products & Services: