E: Engine Oil Tank Breather Advice

[davidd]

Just a thought. If there is a leak from the chain oiler especially if the adjustment screw in the neck is screwed down tight it may be that the pipe from the neck down to the exit from the rear of the tank is fractured inside the tank. If the oil level is above the fracture it will leak out. I had this on a section members bike and I blanked it off as described.

Brian

I worry that I am not describing the chain oiler well when someone mentions tightening the adjustment screw in the filler neck. The history of the UFM shows that there were two tubes used to deal with oil return and providing a breather. On the Series B machines, these two tubes were brazed to the filler neck of the UFM. The tube nearer the drive side was the oil return to the tank. The tube nearer the timing side was an atmospheric breather. The atmospheric breather would guide any oil that exited out the breather tube at the rear of the UFM to the chain.

This remained the same on the Series C models, but with a few refinements. Instead of brazing the return and the breather to the filler neck, a steel block was brazed to the filler neck. The two tubes entered the bottom of the filler neck. The return oil pipe passageway continued straight up to the top of the block, where an adjustment screw was fitted. A third hole was drilled at the bottom of the steel block to allow the oil to return to the tank.

The atmospheric breather tube passageway in the block was drilled halfway up where it stopped. A fourth hole was drilled crossways through the block from the timing side of the block, which is not visible. This hole joined the two passageways for the return oil and the atmospheric breather.

I believe that the adjuster screw for the chain oiler does not have a seat, so it cannot stop the flow of oil from the oil return passageway. It probably just acts as an obstruction in the passageway that gets larger or smaller. Screwing the adjuster down tight will not stop the oil flow to the chain oiler, it simply slows it down as there is no seat to be closed off. Additionally, the oil that is flying around in the filler neck can travel down the hole for the atmospheric breather on the timing side of the steel block. This 4th hole (I have called this a bypass) is a direct path to what we are calling the chain oiler tube (which cannot be blocked off) and the passage continues until it tees into the oil return hole. This is the passage that the adjuster screw is blocking or unblocking.

Apologies to all who understand how this system works as I am beating this dead horse mercilessly, but I did not fully understand how this system worked until Greg Brillus mentioned the Series B arrangement to me. Brian's experience with the fracture is instructive, but ultimately the bypass hole makes the chain oiler tube a breather that can only be blocked by running a drain plug (A26) in the threaded hole at the rear of the UFM. The chain oiler tube cannot easily be blocked from the filler neck.

David

 

[Bobv07662]

When I was investigating my heavy breather I closed the chain oiler screw all the way. At the same time I put a cap on the line going down to the chain. Have never seen any oil in that line, I've checked a couple of times.
As far as the chain goes, it's quite happy getting sprayed occasionally with the drying white spray aerosol lube.

 

[teunvandriel]

Peter Volkers gave me this tip, Peter has ridden much more than 400000 miles with his Rapide, for a long time he used the Scottoiler but since a few years he uses a ceramic chain lubricant "ceramic synthetic chain spray" (see the website), great stuff according to Peter, no more messing around and a big improvement in the life of the chain.

There are people who go for 100% original, they have their Vincent for decoration next to the fireplace, then of course such a tank breather pipe belongs on it. I myself prefer to ride it and already far back in the last century I removed that pipe and plugged the hole because of the grease mess.

I once tried 2 breather pipes at the same time, the timed breather in combination with a V2 breather (a stainless elephant trunk) from Australia. The oil spurted out of the pipe of the timed breather so I quickly removed the pipe of the crankcase breather and screwed a plug in it.
I have never tried such a series D air vent on my C Rapide, but I understand it requires a modification of the upper valve guide.

 

[oexing]

For better breathing via valve spring caps you don´t mod the upper guides, just dremel the channel on the head a bit higher up. My idea was to improve the access of oil to the springs and guide and rely on venting the engine only by a reed type resp. one way valve from the spring cup. No more timed breather from the timing case, not a great place for a breather anyway when you hope to have decent oil mist in there. I would not want an open hose for venting an engine as no vacuum is achieved from this in the engine which helps prevent oil leaks.

Vic

 

[Speedtwin]

Fantastic information thank you.

 

[Speedtwin]

Back to breathing and thank you all, for your patience.
Further investigation during the strip down and investigation of my new to me, Rapide.
The cycle is fitted with a timed breather piped and exiting to the rear nearside nice neat job.
I also have a breather from the front cylinder front spring cap , has a replacement cap with a snorkel again neatly piped to the rear nearside.

Question one Will these two breathers work against each other during the four stroke cycle?
Question two which one to keep if the answer is one or the other?

Thanks
Al

 

[ClassicBiker]

Back to breathing and thank you all, for your patience.
Further investigation during the strip down and investigation of my new to me, Rapide.
The cycle is fitted with a timed breather piped and exiting to the rear nearside nice neat job.
I also have a breather from the front cylinder front spring cap , has a replacement cap with a snorkel again neatly piped to the rear nearside.

Question one Will these two breathers work against each other during the four stroke cycle?
Question two which one to keep if the answer is one or the other?

Thanks
Al

The short answer is yes, they will work against each other. If the timed breather is functional and correctly timed, it will be closed as the pistons rise and create a slight vacuum in the crankcase. If the breather from the front spring cap is merely an open pipe, air will be sucked in, negating the purpose of the timed breather. If the front breather has a one way valve that only allows air to escape, it will be different story. Do you know if the front cap breather has a one way valve of some description?
Steven

 

[Speedtwin]

Thank You Steve,
I shall investigate the line from the front spring cap for a non return valve.
From my poor memory do not recall seeing one.
Will look at the complete line in detail.
Great hydraulic supplier near me so an NRV should be easy to find.
Alan

 

[timetraveller]

Why not try an experiment. Block off one, whichever is easiest to seal up, and then try the bike. Then reverse the blockage to the other breather and try again. You should be able find out whether one is more effective than the other. Good luck with it.

 

[BigEd]

Thank You Steve,
I shall investigate the line from the front spring cap for a non return valve.
From my poor memory do not recall seeing one.
Will look at the complete line in detail.
Great hydraulic supplier near me so an NRV should be easy to find.
Alan

The breather on the front exhaust spring cap was fitted to later models. The cylinder head was also altered by creating a better passage from where the exhaust spring is into the cap. I modified the front head on my Rapide to provide a path for the engine to breathe through. You can do this by hand with a round file or a rotary cutter but it needs to have the head off. You can see photographs of this earlier in this thread, post #24 by oexing. I have a 'D' cap fitted with a breather pipe to the rear of the bike. It has a small non-return valve fitted near to the cap. I have blanked off the timed breather. Good breathers help reduce leaks but if the engine is worn blow-by past the piston makes the breathers work hard so a good breather system is not guaranteed to fix all leaks.
It is worthwhile checking the timing of the timed breather. I think the instructions/numbers are in Richardson if you have the book. You don't need to dismantle the timing side to do this. You can blow through the breather pipe to see when it opens or closes. A timing disc is fitted by removing the brass OP9/2 found near the bottom of the timing cover. A timing disc can be mounted on a piece of 1/4" round bar with the end ground to a very shallow taper can then be tapped gently into the hole in the hollow mainshaft.

The breather valve I have fitted is similar to the one sold by Ben Kingham. He fits them on his racers to great effect. It is inexpensive and y can see it/buy it on his BSK SpeedWorks website: PCV valve link