This is a replacement cylinder for engines with either 98" (1999-'06) or 107" (2007-'16) S&S bolt-in big bore kits. Cylinder fits front or rear positions. Order two cylinders for a set. Cylinders are honed to size for replacement pistons. No piston fitting is necessary unless additional clearance for immediate racing applications is desired. Sold each.
S&S 3.937" pistons are machined to such close tolerances that it is not necessary to measure the piston. Additionally, the low friction coating on the piston skirt of early
production pistons with out micrometer window makes taking measurements very difficult. Therefore, hone cylinders to nominal diameter +/- 0.0001" for correct
clearance. Current production pistons have micrometer windows in the coating on the piston skirts that allow accurate measurements to be taken. These pistons
may be installed by honing cylinder to nominal diameter +/- 0.0001" or by measuring piston and honing cylinder to achieve .002" - .0025" close clearance for street
applications or .0032" - .0045" loose clearance for immediate competition use.