Increases engine compression ratio ot 13.0:1 (stock '06-'09 is 11.2:1 and '04-'05 is 11.9:1) Offers 1.5 to 3 hp increase throughtout most of the power band. No crank rebalancing necessary. Piston is forged aluminum with machined valve pockets for additional valve clearance when higher lift camshafts are used. Includes piston rings, piston pin, and clips (uses stock replacments). GYTR Top End Gasket Kit (GYT-5TG04-10-00) required for installation. Requires use of a minimum 100-octane racing fuel.Note: All 2006-2009 YFZ450R models are regulated by the EPA. Because this accessory affects emissions, using it constitutes tampering punishable by law unless the vehicle is only used in closed-course competition
