Reed valve breather for Big Twin Evolution by S&S - Standard diameter

An S&S Reed valve breather, with pending patent, which effectively resolves the oil blow-by issue in Big Twin Evolution engines. Unlike the rotary valve used in Big Twin engines since the 1930s, the crankcase breather Reed valve does not rely on the crankshaft to open and close. Consequently, the opening timing is not determined by the crankshaft position. It is governed by the pressure differential between the crankcase and the cam chamber. The Reed valve closes when the pressure in the cam chamber is equal to or greater than that in the crankcase. This operational difference is significant, as the ideal opening frequency varies with engine speed. By opening and closing "on demand," the Reed valve automatically compensates for air mass lag when expelled from the crankcase. This is particularly significant at high RPMs, where the expulsion time is minimal. This "on demand" operation also allows the valve to accommodate larger compression volumes. The installation of the S&S Reed valve has literally stopped oil at high RPMs in test engines with severely worn rings. This Reed valve replaces the original rotary valve in Big Twin Evolution style engines. Installation is easy and straightforward. The breather pinion is removed, and the new Reed valve is inserted into the cavity. No alignment marks or rotating parts are required. The valve can also be used in engines with minor damage to the breather cavity, and an oversized +.030" valve is available for engines with greater damage. For all Big Twin Evolution engines 1993-2000.


Specifications


Pack
1


HS Code
8714109090


Origin
US


Motorcycle family
Dyna | FXR | Softail | Touring