YFZ450R YFZ 450R Big Bore Kit 98mm 478cc 13.51 CP Forged Piston Top End Rebuild

  
YFZ450R YFZ 450R Big Bore Kit 98mm 478cc 13.5:1 CP Forged Piston Top End Rebuild. Upgrade your YFZ450R or YFZ450X with a 98mm 478cc big bore kit delivering high compression performance and durability. Yamaha YFZ450R / YFZ450X 98mm 478cc Big Bore Top End Kit CP Cometic 13.5:1. Transform your EFI Yamaha with the BPRATV 98mm 478cc Big Bore Top End Kit engineered for riders who demand aggressive power, instant throttle response, and proven durability.

Built around a forged CP-Carrillo piston, a performance-plated BPRATV Nikasil cylinder, and a precision Cometic MLS gasket, this kit boosts displacement to 478cc with a race-focused 13.5:1 compression ratio for explosive performance. Designed as a complete, race-ready solution, this big bore kit delivers reliable power gains with OEM-plus fit and finish for high-performance riding and competition use.

98mm big bore increases displacement to 478cc for massive torque gains. 13.5:1 compression for harder hit, stronger midrange, and top-end pull. CP-Carrillo forged piston for high-RPM stability and long service life. Nikasil-plated cylinder for superior heat transfer and wear resistance.

Cometic Top End Gasket Kit with a Big Bore Cometic MLS gasket ensures reliable high-pressure sealing. Precision-engineered for Yamaha fuel-injected 450 sport ATVs using a direct big bore replacement top end. Yamaha YFZ450X EFI - All Years. Replaces OEM top end with 98mm big bore components. Designed for race fuel use due to high compression.

Professional installation and EFI tuning recommended. Q: Do I need tuning after installing this kit?

EFI fuel and ignition mapping must be adjusted for the 98mm 478cc setup. Q: Will this work with a stock cylinder head?

It is designed to run with a healthy stock head and valves. Q: Can I run pump gas with this kit? Due to the 13.5:1 compression ratio, race fuel is required. At BPRATV, our promise is unwavering: The Best Parts.

Every kit is carefully selected and built to deliver proven power, precise fitment, and race-level reliability. Trust BPRATV to keep your Yamaha YFZ450R/X running at its best, every single time. Upgrade your YFZ today and feel the 478cc difference on your next ride.

BPRATV - The Best Parts. This product is exempt from the emission standards and related requirements of 40 C.

§ 1051 as provided by 40 C. § 1051.620, and California law. DO YOU NEED THIS ITEM INSTALLED? NOTICE REGARDING PHOTOS: Product photos used in our listings are for example only to show the high quality of our components. You will receive the correct quantity, size, and fitment of bearings, titanium fasteners, nuts, and bolts for the specific kit listed. BEARING NOTICE: In some cases, you may receive SEALED bearings. If your application requires an OPEN bearing, the seals can easily be removed. EMISSIONS & RACE USE ONLY: This product is exempt from emission standards and requirements of 40 C. § 1051.620, and California law e. Vehicle code §§ 27156 and 38391. BPRATV LLC shall not be liable for specific, incidental, or consequential damages (loss of property, equipment, profits, or revenue) resulting from sale, installation, or use of these parts. This product is NOT DIY; we strongly recommend work be done by a qualified, experienced mechanic. Items installed or prepped (lubricated/sealed) are ineligible. Titanium Fasteners: Failure during use results in replacement only.

INTERCHANGEABLE PARTS: We may substitute parts of equal quality from different manufacturers to prevent backorder delays. Prices and listings subject to change without notice.