Wiseco K1670 3-5/8 big bore piston kit Harley Evo Softail Touring FXR Dyna 88"Wiseco K1670 is a forged 3 5 8" big bore piston kit designed for 1984 1999 Harley Davidson 1340 Evolution engines, increasing displacement to 88 cu. in. (1438cc). This kit features 9. 25: 1 compression ratio flat top pistons, includes ring sets, wrist pins,missing two wrist pin clips and requires cylinder reboring. Key Details for Wiseco K1670: Engine Fitment: 19841999 Harley Davidson 1340cc Evolution. Bore Size: 3. 625" (Standard big bore).