ET: Engine (Twin) Breather help please

[davidd]

The only comment I would make about the Series D breather is that the Series D head was designed differently from the Series C head to make the cap breather work properly. I believe that there was a gap in the top valve guide seat of the D head that allowed air to pass by the upper valve guide to the breather hole in the cap. I believe that the top valve guide (ET40) is unmodified as used in the Series D head.

David

 

[vibrac]

I am always amazed at the volume of posts the word breather evokes. My reply is simple Ben took his legally mandated oil catch tank off the racer last week after an entire season of racing including the Goodwood races it was BONE DRY. His system comprises two PCV valves front exhaust cap rear exhaust cap the valves are available from Ben or the Spares company (PCVVALVE) a bit bigger than your thumb the engine is a D so no timed breather anyway. another common mistake is that with a PVC system the pipe has a lot of air passing up and down it doesent after a few seconds running a level of air pressure in the crankcase is established and little or no air travels along the pipe. PCV valves ideally should be mounted upward if space allows.

 

[kerry]

So we have 3 alternatives as I see it, Bens system seems excellent even though the PCV valves cannot face upwards ?
Next we have the Ugly but good Elephant which can have a PCV valve facing upwards, both with the timed breather blocked off.
My bike now has the slim Elephant with thin pipe and a PCV valve, will that be OK or should I and others choose Bens system or large Elephant ?
Or should I go back to the timed breather alone with a PCV valve as my Engine is in good condition !

 

[vibrac]

As I said kerry the pipe on a pure PCV valve system carries nothing after a short start up period* so small pipe is OK

* many amusing tales of the french letter experiment on a breather pipe ... it never exploded!

 

[kerry]

Thank you Tim, appreciated.
Kerry.

 

[brian gains]

Best to plug the timed breather thread as its place is unfortunate when air gets expelled from a place that is loaded with oil mist. When having a breather device from there you better have a long hose climbing up from there and have a reed type one-way-valve at the upper end of the hose. So any minimum oil drops in the hose got a chance to drain back into the engine and no real oil will end up in free air. Actually there is not a huge air flow from a breather provided the engine is not very sick or other places draw air in at poor seals.

Vic

what am I missing, if it's a timed breather how will any accumulated oil mist drai back into the motor?.

 

[vibrac]

what am I missing, if it's a timed breather how will any accumulated oil mist drai back into the motor?.

With a PCV valve the air flow will be minimum so oil will fall back under gravity in my experience most oil only expelled on start up period when there is air flow.
The other phrase is "if engine is not sick" any piston blow by may not adversely be noticed in use but will pressurise crankcase and force an oil laden air flow

 

[kerry]

I have just been out on this Shadow for it's first run since blocking the Timed and just having the slim Elephant with a thin pipe running to the rear with a PCV valve halfway along.

Not even a tiny spec of oil at the end. So I am pleased I done it as per Vibrac's suggestions, very grateful to him and other comments.

When it had the pipe from the timed as well as the Elephant that now blanked pipe had white frothy stuff in it and a very small amount from the end, I was not happy with that.

My friends are looking underneath the Shadow and the Cock bird has said to the female 'look no oil leaks'

Kerry

 

[Vincent Brake]

An Elephant has its trunk down guys....

 

[Bernhard_Austria]

An Elephant has its trunk down guys....
View attachment 59811

It works pretty well on my twin too