S&S 98 Big Bore Piston Kit For Harley Looking to get more out of your Harley Big Twin These S&S big bore pistons convert compatible 88 engines to 98 displacement while working with the stock 4-inch stroke flywheels. Designed to deliver 10.3:1 compression with stock heads, they bring proven S&S performance engineering to your engine build. Features: Works with stock 4 stroke flywheels to increase displacement from 88 to 98 Stock cylinders may be bored to accommodate larger pistons, but S&S recommends using their 3.937 bore cylinders, which feature high-strength alloy cast-iron liners 10.3:1 compression using stock heads Pistons are complete with rings, wristpins, and wristpin clips 3.937 standard bore