Reply To: Lauson T651 Breather Assembly

[frankr]

Thinking back to my old lawn mower days now.  Any engine will have some piston /rings blowby when running.  That blowby would pressurize the crankcase if not allowed to escape, causing, among other things, seal leakage and sludge formation.  The simple breathers used on mower engines is just a check valve disk which opens with pressure and slaps shut with partial vacuum.  I guess the shut phase does allow some bypass.

 

Of course, all that is illegal with modern engines where vapers are no allowed the escape to the atmosphere, but are re-routed back to the intake manifold for burning.