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S&S Crankcase Reed Breather Valve For Harley Evo Big Twin 1993-1999

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S&S Crankcase Reed Breather Valve For Harley Evo Big Twin 1993-1999

If you're fire-breathing stroker monster keeps weeping oil, perhaps your weak plastic rotary gear is to blame. S&S developed this reed-style breather that has no gear - crankcase pressure actually opens it up. Installation is a snap - slide it into the cavity, and button your cam chest back up. There are no marks to align, and no rotating parts. Thoughtfully, S&S also offers this part in an .030" oversize version for those who have scored cases from their nylon breathers. If that's the predicament you find yourself in, you can have your machinist open up the breather bore, install the Reed Breather Valve, and put your engine cases back into service!


  • New-style breather is not dependent on the rotation of the crankshaft to make it open and close; instead, reeds open when the pressure in the crankcase becomes greater than the pressure in the cam chest and close when the pressure in the cam chest is equal to or greater than the pressure in the crankcase
  • By opening and closing "on demand," the reed valves automatically compensate for the 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 USA
View Fitment Notes & Exceptions

Fitment Notes & Exceptions

This is a universal fit part; it may or may not fit without modification.

  • These parts require a good deal of technical skill to install correctly - it is the responsibility of the person assembling the parts to check all clearances and assembly specifications
  • Item is for head-breathing engines only - please verify before ordering
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Product Style RevZilla Item # Manufacturer Product # Availability
Standard 958845 312100 Available: Expect 1-2 business days processing time prior to shipment
+.030" Oversize 958844 312096/31-2096 In Stock: Usually ships in 1-2 business days