ET: Engine (Twin) Breather help please

[kerry]

The Shadow I bought in January has 2 breathers fitted, a elephant style one but very thin slim body compared with the original and new ones from our spares co.
My concern is this sufficient to allow breathing being so small with thin pipe too. ?
It is suggested the timed breather should be blanked off, this currently has a PCV valve at the rear of the bike next to the one from the trunk
I am told the PCV valves should be close to the front not at the rear, currently I get virtually nothing dripping from the ends, but if I just have the slim breather will that be enough on it's own or should I fit the bigger type with larger bore pipe ?

 

[timetraveller]

lI think that there is some incorrect information here. The breather where the normal timed breather is does not look like a Vincent item and I would be surprised if the Spares Company supplied it. That very thin pipe coming off the side of the' banjo' connection is not normal but considering that the normal banjo bolt only has four small holes it is possible that the area inside the small pipe is adequate even if it does not look to be so. The 'elephants trunk' is no such thing. It appears to be just a small, hollow right angled connector. The elephants trunk device is much more elaborate. If one were to fit a one way valve to anything it should be to the 'elephants trunk'. The timed breather already has a device inside it to stop it sucking air in when the pistons are going up, hence the word timed. It is of course possible that this unfortunate mess has been created to overcome the fact that the timing of the breather is wrong or has slipped and there have been plenty of items on these pages as to how the timing of the original timed breather can be changed and improved. I would check the timing of the breather by removing the PCV valve and then blowing into it to see when the internal timed breather is actually open. You will need to take off some or all of the tappet inspection caps to determine the position of the valves and pistons.
A word of warning here is that none of us knows it all and it is possible that the previous owner of this bike was an expert in fluid flow dynamics and has created something here that works perfectly and is a vast improvement over what we have been doing over the last seventy odd years. If that is not the case and they have totally failed to understand what is supposed to be happening here I would suggest that you check the rest of the bike over very carefully,

 

[kerry]

Appreciate your reply but I am not suggesting any of these parts came from our spares company which is part of my concern,
Does anyone recognise this thin type elephant breather and is it capable of doing the job on it's own with the timed breather being blanked of which is what the spares company suggest when fitting their larger in body Elephant trunk which also has a much larger exit pipe. ?

 

[oexing]

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

 

[kerry]

Thanks Vic, I have now blocked off the timed breather and just have this unknown ? smaller Elephant type which I hope will be able to breath enough on it's own being much smaller than our spares ones or the originals from Ron Kemp ?

The engine did have a re bore and pistons etc from the spares company and is in good order, starts first or second kick, no oil leaks or smoke, I am very pleased with it but was told it was wrong to have the 2 breathers working against each other.

 

[Chris Launders]

If the PCV valves are mounted the right way they would not be working against each other, but rather with each other.
I personally have the standard timed breather and a breather off the front inlet tappet cover with a PCV on both my Vincent and Norvin.

 

[kerry]

Chris, .
I was told by a top engineer and a very top forum person who also races Vincents that it is wrong to have both as mine was, the spares company obviously agree because when buying an Elephant one from them they recommend blocking the timed and give the part number for this, I really am no expert hence asking for advice and thankful for it. I was told the way mine was they would be fighting against each other !
Kerry.

 

[davidd]

I believe that what you are calling the "slim breather" is just a mag inspection cover with a hole and a right-angle fitting. You are correct that the small size diameters of the piping will cause the air/oil to move at very high speeds relative to the larger pipes or the Elephant breather.

In theory, you can have all the atmospheric breathers you wish, but if you have some type of check valve breather, like a PCV valve, a reed valve, or a timed breather, you should run only one breather. The valved breathers are trying to create a vacuum inside the cases and the vacuum will simply suck air in through any hole or atmospheric breather if it is installed with a valved breather.

The timed breather works well if it is timed properly and the mods have been done on it that Phil Irving recommended decades ago. Atmospheric breathers are usually added when the top end is worn enough to need a rebuild.

Breathers do the most work at low speeds when the pistons are moving large amounts of air slowly. At high RPM the pistons are reversing quite fast and the crankcase pressures rise and then reverse very fast, which provides a bit of equilibrium.

David

 

[kerry]

I now have blanked the time breather as recommended with an Elephant, have a non return valve fitted to the pipe from my slim elephant.
With the end of the pipe put into fluid it bubbles on tickover but hardly at all on faster running as you say giving equilibrium.
I think best now to fit the correct large Elephant perhaps or maybe as my engine is in good order I should just go back to just the timed breather with no valve fitted and run the pipe upwards and into a cup or rear chain
Thank you David,

 

[Speedtwin]

When fitting pcv valves, valve position is important, it is best to allow for the misted oil to run back under gravity back into the ventilated space rather than gather in low lying pipework.
When running a trunk I would blank the timed breather.
Don't use the trunk as it looks bad man.

When not running a trunk I leave the timed breather piped to back wheel as per KNB that's

my bike in the picture.
Please note the small touring tool kit on the rack/pillion seat.
Confident man...

The front spring cap I have ventilated with a pcv hidden behind the wheel pump again pipe to rear of bike.
Route from front cap north to rhs then along under tank secured to pump between cab down between engine and swing arm and along to breather set up.
Lovely job.
Works great I am oil leak free no pressure build up and no oil out the back at all.
Took a while to work it out and it works great very similar to Chris s set up.