Athena S5F08300002B 83mm Big Bore Piston Kit for 290cc Engines - 12.5:1 Compression Ratio, Oversize Upgrade from 82.96mm | High-Performance Engine Rebuild & Motorcycle Racing Parts

Bore: 82.96mmCompression: 12.5:1 CompressionSizing: OversizeAll pistons are forged using a precision heat-treatment process that allows for production tolerances of just .005mm. Forged piston kits are available in A, B and C sizing. Forged piston tooling allows for the lightest available product. Kits include antiwear coated piston, rings, pin and circlip. Made in Germany.This item fits the following vehicle applications:compatible with Yamaha WR250F 2011-2012compatible with Yamaha WR250F 2001-2009compatible with Yamaha YZ250F 2001-2007