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For maximum piston and ring life, fit pistons using close fit dimensions. Close fit requires absolute adherence to new engine break-in as described on page 7. 2. For immediate drag strip use, fit pistons using loose fit dimensions. Break in rings and pistons with 50 easy miles if possible. Piston and ring life will be reduced with loose fit dimensions. 3. Measure all pistons at widest point across thrust face, perpendicular to wristpin hole. Several measurements should be taken to locate widest point. Typically, this will be at bottom of piston skirt for pre-1984 big twins, and approximately 1⁄ 2 ” below level of wristpin hole in pistons for Harley- Davidson®Evolution®and Twin Cam 88®engines. If pre-1984 piston is notched for placement in rear cylinder, use measurement directly above notch for skirt measurement. 4. S&S®recommends #220-#280 grit stone for final honing of stock bore and Sidewinder®, S&ST124 and S&S big bore cylinders. #320 grit stone is recommended for engines using S&S 92-4500, 92-4510, or 92-4520 pistons. 5. Follow procedure recommended in Harley- Davidson®service manual for boring and honing stock bore big twin and Twin Cam 88®cylinders. Follow instructions included with S&S Cylinder Torque Plate Kit when boring and honing S&S 35⁄ 8 ” or 4″, 41⁄ 8 “bore cylinders. Torque plates must be used to simulate compressive stress in an assembled engine. Cylinders will distort if torque plates are not used.
