S&S CYCLE 3-1/2″ +.010″, 80″ LC Forged Pistons for ’78-’84 HD OHV Engines – 106-5512

These 3-1/2″ +.010″ bore pistons fit 1979-’84 80″ HDbig twin engines, producing 8:1 compression with stock unmodified cylinder heads.. The modern alloys used in these pistons, coupled with the advanced skirt profiles, allow them to be fit tighter resulting in low engine noise and long engine life. In the past, this could only be achieved with weaker cast pistons. S&Swill fit these pistons to your existing cylinders (when purchasing new cylinders, pistons can be fit to them as an option)

• For 80″ stock big twin motors
• Forged pistons for superior strength
• Piston kits include set of pistons, rings, wristpins, and clips
• Wrist pin deck height 1.270″
• Made in the U.S.A.
• Require the use of connecting rods with a rod length of 7.440″(standard length OEM #24281-74A connecting rods); use of earlier connecting rod with rod length of 7.470″ (OEM # 24281-41A) will result in a slight increase in the compression ratio of about one-halfpoint, and may also result in clearance problems (check all piston to cylinder head clearances carefully when using early style rods).

  NOTE:Since many older motorcycles have been modified, be sure to confirm that your engine is still stock before ordering replaement pistons. Using 80″ pistons with 74″(331/32″ stroke) flywheels will result in very low compression and poor performance. Using 74″ pistons with 80″(41/4″ stroke) flywheels will result in contact between piston and cylinder head, and potential engine damage. S&S offers machine shop services through the S&S Service and Speed Center. New pistons can be fit to existing cylinders for a reasonable charge

Fitment Guide

Specs