Reed valve engine breather.

[toglhot]

I machined up this reed valve engine breather for the TX650. The petal was half of a petal from a generic reed valve I bought on ebay. The rest I machined up on the mill.
Reed valve breathers allow air in the crankcase to be expelled on the pistons downstroke and drastically slow the flow of air being sucked back in on the pistons up stroke. thus maintaining negative crankcae pressure. As a secondary positive, they also prevent excesive pressure on the piston on its downstroke and prevent some oil seapage through jointing surfaces.

 

[ChevyEFI]

Is this a known / suggested addition for that engine? Is any effort made to prevent oil loss, such as by a catch can in the exhaust side of the breather circuit? My interest is not in that engine; more so in later model stuff that switches oil circuits for valve operation control.

 

[toglhot]

All modern engines have PCV valvess (positive crankcase venting valves). Recirculating blowby gasses from the crankcase through the induction system, became standard practice sometime in the 70s/80s as a result of pollution concerns. Prior to that, engine blowby gasses were simply vented to the atmosphere by a tube exiting the crankcase/rocker coiver wiithout a valve. Without a PCV, when the piston is on its upstroke it draws air in through the breather, then when the piston is on it's downstroke it acts as a pump expelling that air, along with the blowby gasses, putting pressure behind the piston. Engine breathers can be vented to a catch can or recirculuated through the induction system, I chose the latter thereby negating the need for a catch can. It is simply a cleaner more efficient deign. Blowby gases contain particles from the combution chamber, if not expelled they mix with the engine oil.