S&S, Standard Steel Breather Valve and Spacer Set

With steel breather valve spacer set for correct axial play. High-quality steel breather valve for use as an original replacement or high-performance part.
Note: S&S breather valves come with elongated breather holes to increase the duration of the vacuum, allowing more oil to be drawn out of the cylinder heads. This has no downside on any model year, whether stock or Big Inch engine.
Note: An oversized .030" breather valve (531238) is available to salvage worn or damaged crankcases. A JIMS breather hole reamer (MCS 978343) will ream the damaged hole to +.030" so a +.030" breather valve can be used.
Technical tip: The opening timing of the S&S breather valves, for late 77-84 Shovel and 84-99 Big Twin Evo models only, was changed by S&S in the year 2000. This is done to improve oil scavenging and reduce oil carry-over in high-performance, large-displacement engines. The old opening was at TDC and closing at 65° after BDC. The new opening is at 17° after TDC and closing at 82° after BDC. The old timing specification can be obtained by installing the timing mark on the breather gear one tooth clockwise from the timing mark on the camshaft gear. In addition, the oil drain hole in the breather cavity (opposite the drive gear), which was previously round, has been elongated (made longer) to increase the duration of the suction to the crankcase breather 'settling' cavity. The new specifications are not useful on most original engines, but they are harmless. The breather windows in S&S crankcases will typically open at 7° after TDC and close at 92° after BDC. Builders using other crankcases can modify the crankcase breather opening to achieve these specifications and obtain maximum breather efficiency and performance.


Specifications


Brand
S&S


Application
L77-99 Big Twin (NU) (Excl. TC)


Sales unit
Kit


Material
Steel


Packaging weight
0.218 kg


HS Code
84099100


Motorcycle family
BIG TWIN, DYNA, FX, FXR, SOFTAIL, TOURING


Original name
S&S, steel breather valve & spacer set. STD.