S&S CYCLE REED VALVE, 84-99 +.030 31-2100

New-style breather is not dependent on the rotation of the crankshaft to make it open and close. Instead, reeds open when pressure in the crankcase becomes greater than pressure in the cam chest, and close when pressure in the cam chest is equal to or greater than pressure in the crankcase By opening and closing "on demand," the reed valves automatically compensate for lag time associated with accelerating the mass of air as it is forced out of the crankcase, increasing performance and stopping high-rpm oil carryover in engines with marginal piston ring seal Installation is fast and simple; no aligning timing marks, and no rotating parts Made in the U.S.A.