100" | 109" Monster Big Bore Kit / EVO Motors

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The Revolution Performance Monster Big Bore Kit takes an '84-'99 Evo Big Twin out to 100 or 109 cubic inches on aerospace grade plated cylinders. Displacement is the most direct ro ute to power on an Evo motor, and Revolution Performance built these kits around that idea. Instead of sleeving a stock casting, the Monster kits use all aluminum cylinders with a nickel silicon carbide bore plated straight onto the aluminum. That one decision opens the door to a larger bore, cuts friction inside the cylinder, and pulls heat out of the top end faster than an iron liner can manage. How the Monster Big Bore Kit Builds Power A plated bore runs cooler and slicker, which shows up as horsepower at the rear wheel and as a longer service life for the whole top end. Wiseco forged pistons arrive matched to the cylinders, so bore and piston come as a designed set rather than a stack of parts you hope work together. Rings, wrist pins, circlips, and performance head and base gaskets are all in the box. Replacement gasket sets are sold separately for when the motor eventually comes apart for service. Every kit is manufactured in the USA. Monster Big Bore Kit Specifications Fits '84-'99 Evo Big Twin motors Available in 100 cubic inch and 109 cubic inch displacements 100 inch kit requires 4 1/4" stroke 109 inch kit requires 4 5/8" stroke Aerospace grade all aluminum cylinders with nickel silicon carbide electroplated bore Wiseco forged pistons with rings, wrist pins and circlips included Performance head and base gasket set included Finish: natural silver, or black with highlighted fins Made in the USA Installing the Monster Big Bore Kit All kits require case boring, so this belongs with a shop that has the equipment and the experience to do it correctly. Whoever assembles the motor is responsible for checking every clearance and assembly specification before it runs. Complete Your Evo Big Bore Build Evo parts get harder to find every year, so if you don't see what your build needs, ask us. New to big bore work on an Evo? Start with our big bore kit guide. Tuners & Fuel Systems — carb jetting or EFI tuning after the swap Big Twin Parts — Evo-era engine hardware Gaskets & Seals Engine Tools Oil, Filters & Lubes — break-in oil Shop all Revolution Performance Show more