S&S, steel breather valve. +.030" OD

Oversized steel breather valve +.030". Used to salvage worn or damaged crankcases. Suitable as a stock or high-performance replacement.
Note: JIMS has a reaming tool for +.030" breather holes, available as reference 978343.
Note: Steel breather valves require steel spacers. Plastic ones require plastic spacers. Do not mix steel and plastic parts.
Note: S&S breather valves come with elongated holes to increase vacuum duration, allowing more oil to be pulled out of the cylinder heads. This has no downside on any model year, either stock or Big Inch engines.
Technical tip: The S&S breather valve timing, for late-model 77-99 Big Twins only, was modified by S&S in the year 2000. This was 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. Additionally, the oil drain hole in the breather cavity (opposite the drive gear), previously round, has been elongated to increase the duration of suction in the crankcase breather 'settling' cavity. The new specifications are of no benefit in most stock engines, but are harmless. The breather windows in S&S crankcases 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 for maximum breather efficiency and performance.


Specifications


Brand
S&S


Application
L77-99 Big Twin (Excl. TC)


Material
Steel


Packaging weight
0.178 kg


HS Code
84099100


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


Original name
S&S, steel breather valve. +.030" OD