xbacksideslider
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- Aug 19, 2010
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Towner said:Hello,
I read much about PCV valves in this forum and I already discovered teh typical oil leaks at my Commando.
Normally the breather hose is connected to the air filter, but most owners (as I) disconnected it to avoid soiling the filter.
But the PCV system (positive crankcase ventilation) wasn't only introduced to avoid pollution, but also the intake suction should
take away the blow-by gases and additional generate the negative pressure in the crankcase.
So my question is:
Do the oil leaks appear because the breather hose is not connected to the air filter ?
Ralf
No.
There is insufficient vacuum in the air box to pull useful vacuum at the other end of the breather hose.
Automotive PCV valves typically are ball valves, using a steel ball to stop an orifice. As such, they cannot react as precisely or quickly as a reed valve.
That is OK in an old worn out multi cylinder car engine with offsetting internal pressure/falling piston pulses where the problem is constant blow by that likely holds a ball valve constantly open.
Our two pistons move together, creating huge pressure and vacuum pulses. As revs rise, a steel ball valve likely beat itself up and would just flutter in response to our quick rise/fall, reversals, of pressure pulses.
A reed valve, located as close to the crankcase as possible, is the answer if you want to create an average low pressure condition in the crankcase.