FT: Frame (Twin) Elephant trunk breather

[greg brillus]

Bernd..........I think apart from widening the slot in the rotating breather pinion, it was more just making the outlet fittings larger in bore size. So instead of having the standard 1/4" passageway with restrictive banjo's, I used a straight nipple outlet with a larger bore size into a short length of 3/8" (10 mm) flexible hose, this then passed downward and into the lower front corner of the kickstart cover via the hole where the brass abutment for the kick start stop buffer/spring arrangement. The thing to remember about breathers is you are only really venting the excess crankcase pressure, that is, leakage past the rings. The timing chest is not really a good place to have a breather full stop, as there is quite a lot of oil flinging around when the engine is running. Most modern engines have breathers that are kept away from areas where quantities of oil can interrupt the outward flow of breather fumes. They generally draw these fumes into the intake manifold somewhere. Vincent engines and their breathing symptoms will always be a bind for owners..................

 

[john998]

Hello, yes quite agree, not a thing of beauty. The one on the solo did reduce the oil consumption noticeably, this engine has a good number of miles on it. The open pipe on the outfit one is a little noisy, but not a problem, it croaks at you at kick over. The outfit has low oil consumption, even though working harder due to lower engine miles. John.

 

[A_HRD]

I've used an elephant-trunk breather for over 30 years on my Rapide - ever since Mac Read first designed and manufactured them. Yes it was noisy at first, but I simply put a a cylindrical "silencer" from some pneumatic equipment (compressor?) on to the end of a right-angled piece of heater hose and tucked it up in the tank cutaway above the front carb. I can hear the muted "ploppety-plop" of the ball (from a roll-on deodorant!) when ticking over at traffic lights, but not once I'm under way at 10mph. The "silencer" is plastic (about 2.5 inches long and 1 inch dia) with multiple slots - and gauze inside. Incidentally, it has NEVER been contaminated with oil, just road dirt.

Yes it is pig ugly. But I'm with Albervin here, a happy motor is better than an unhappy pretty motor. That said, I have been known to revert to standard in about 5 minutes when "Showing" the bike. But as Greg says:- 'each to his own'.
Peter B

 

[oexing]

Well, I say the elephant-trunk breather is a particularly poor design, ugly too, as it is placed in that open space that everybody looks at. Secondly it is venting a very oil loaded space so you have to care for any oil mist that may find it´s way out of the huge hose that must lead somewhere. I fabricated some breathers of the reed type like in the photos that you stick up the end of some small hose you could place out of sight. As it is a one-way type you will not observe much oil loss because there is only a small amount of air that passes, from piston ring blow-by mainly, provided trhe engine did not suffer a holed piston but then the breather is your smallest problem.
When hiding the hose somewhere - under the tank or seat - it is a good idea to have the reed valve at the end up high, so any drops of oil can drain down the hose back into the engine. The pictured valve is made from 12mm stainless, drilled 6mm , 3mm screw for reed and milled flat for the .10mm / 4-5 thou feeler gage blade to seal at the narrow faces around the Dremeled chamfered opening. The reason for the Dremel chamfer operation is to reduce the contact faces in case some oil mist gets there as oil makes the reed blade to stick a lot and much more pressure is required to force the reed blade to open. As I said, this small valve is all you need, there is normally not much air to be vented from a one way valve on a healthy engine. When thinking about a good place to fit a hose I´d go for the rear cylinder inlet valve spring cover - out of sight and not much oil flying around there. To help the crank case air to vent into that hose I did open up a window around the upper valve guide, see photo, all guide windows done on both heads of course, in order to care for better access of oil to the twin valve springs. These spaces seem to have been ignored lubrication-wise.

Vic

 

[A_HRD]

Secondly it is venting a very oil loaded space so you have to care for any oil mist that may find it´s way out of the huge hose that must lead somewhere.

Ah, but you may not be aware that the stainless cylindrical tube on top of front exhaust-spring cap is in fact a condenser. The incoming air/mist is sent to and fro in "Letter S" fashion. 100% of the mist condenses out into a sump and aided by gravity, as well as suction from the improved crankcase partial vacuum, goes down a 1/16th drilling via valve-spring, rocker and extra oil for the front cam.

It works as well today as it did 30+ years ago. It's still pig-ugly though!

Peter B

 

[john998]

To silence the Ivan Caffery set up I used foam rubber rolled into a cylinder and cable tied on . With the reed valve it is not necessary. John.
As an after thought tried to measure the crankcase pressure on the outfit, this is the one with the silicon hose, at start up it shows about one psi .
This quickly goes to a slight vacuum, difficult to measure but enough to pull water into the engine! It needed an oil change anyway.

 

[vibrac]

Never understood all the wordage about breathers there must be a million posts on the subject just search elephant or breather
A few quid for an inline valve no wider than a pipe placed in the correct position and job is done

 

[oexing]

Sorry, I did not add that photo below, showing the window around the upper valve guide, done to ALL valve guide surrounds. My idea was mainly to get more oil thrown off the rocker onto the upper valve stem and twin springs that are not free from rubbing each other. Then the second target was providing a good access of crank case air venting into any hose that is connected to spring caps with their reed valve at the outer hose end.
Concerning condensation, I guess this mod cannot do much harm, possibly even be helpful, as the space above the springs is normally pretty isolated from the rest of the crank case air. It is hard to imagine there to be any (water?) condensation above the exhaust valve, at this very hot place ??? Maybe this is only a factor for bikes that get just short distance uses - bad for any engine and best to be avoided.
Hose length leading to a one way valve is not a real factor when you think about all that engine case air volume compared to a small hose . You do not need to fit big hoses for one way valves as there is only a very modest air flow when under way.
The big bonus with breather valves is the small vacuum in the crank case when there are a few places in the engine that contain doubtful seals - dynamo - magneto - main bearing scroll bush - valve lifter - any more ?? Valve types with sizeable weight internals are best avoided, pulsation is just too fast to handle that. So the reed type, simple to copy, has best characteristics and is tested since decades.

Vic

 

[Black Flash]

As Peter B rightly said it is pig ugly but it certainly works!
Still not my cup of tea.
There must be something more pleasing to the eye.

 

[timetraveller]

Nothing much is being said about the 'duck bill' one way valves that were mentioned a year or so ago. Apparently these are supplied with some of the Indian made Enfields and consist of a thin rubber tube which is shaped as a flattened slit at one end. Exactly the same principal is used on most boat toilets where they are called 'joker valves'. In the toilet case they are larger, about 40 mm diameter to let waste pass through in the outwards direction and prevent sea water going in the other direction. Many thousands, possibly hundreds of thousands, of these are produced every year and they just work. Has anyone on this forum actually used one of the Enfield ones and did you find it useful?