Comet Breathers

davidd

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My crude understanding of the UFM is that the oil enters at the middle of the bottom of the tank from the oil line that comes from the top of the rocker arms. The oil does not really enter the tank itself, but enters a steel oil line or tube that runs up to the oil filler spout. This oil line enters the little steel rectangle. This steel rectangle is really a splitter or diverter. The oil that enters the bottom of the tank spits out a hole in the steel rectangle. This is where the oil really enters the tank. In the top of the rectangle there is a screw (needle valve) with a spring. The screw or needle meters the oil that flows into a second tube at the bottom of the steel rectangle. This tube goes back to one of the two fittings on the rear of the UFM. In fact, it goes to the right hand side fitting that runs to the chain. By adjusting the needle in the opening of the oil tank you can adjust the amount of oil that is diverted to the chain. So, there is either oil in this tube because you have allowed it to flow through the needle valve, or the valve is closed and there is no oil flowing to the chain. Whatever oil does not go to the chain simply falls into the tank.

I think what Stumpy is saying is that of the two tubes in the UFM one is always carrying oil, the return, and the other,the chain oiler, is always carrying oil or it is closed. Neither can pass air as they are intended to be used. I suppose the chain oiler could be made to pass air, but its designed to be filled with oil so its location and the way it is designed would have to be changed. I have always thought that all of the UFM's (except the D) had the same plumbing.

David
 

ogrilp400

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Not on a B series. A B does not have the rectangular steel block with the adjustment screw. The B series only has the two pipes, one returning oil from the engine. The other is the breather that can contain a lot of oil at times particularly if the oil level is too high.

Phelps.
 

greg brillus

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Interesting points made so far.....can anyone relate to this....Series B type UFM with the normal oil filler cap complete with vent hole clear and unobstructed. Initially ran with the chain oiler pipe fitting at rear of UFM blanked off. At speeds over 80 mph on the highway, would cause oil to spew out of cap area and all over the fuel tank. I then opened the blanked off fitting and plumbed it just above the swing arm pivot area with a T fitting into the existing D type beather cap outlet line using a larger bore fuel/oil hose and ran to the rear next to the axle, this fixed the oil over fuel tank problem, and the pipe at the rear only drips the odd drop of milky oil after a descent run. The oil tank is only filled to just above the steel bridge plate, visable down the filler neck. The reason this all came about was due to the chain being over oiled in the first place.............Cheers......Greg.
 

davidd

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Not on a B series. A B does not have the rectangular steel block with the adjustment screw. The B series only has the two pipes, one returning oil from the engine. The other is the breather that can contain a lot of oil at times particularly if the oil level is too high.

Phelps.

Fair enough, you've got me there. But I would argue that this is a really poor vent pipe. There is no effort to separate the oil from the air as in the oil cap vent (and even that fails at high revs.) So, you have your choice of a vent pipe that passes oil and deposits it on your chain or a metered oil pipe that deposits an inconsistent amount of oil on your chain. I will say that there is rarely a catastrophic condition caused by high pressure in the oil tank, as far as my experience goes. On the other hand, pressure in the crank case is almost always caused by ring leakage.

Taking the major cause as ring leakage, the timed breather is at a distinct disadvantage. It works well only if your rings work well because it is mechanically closed even if the pressure in the crank case remains high. Racers can also have ring flutter at high rpm's and cause momentary instances of high pressure. The check valve breathers work well at low rpm's, but the higher the rpm's the worse they get. Sometimes the ball is too heavy to match its cycle to the pressure cycle. However, for normal street riding they seem to work well and they are inexpensive.

On the racer I have used both the timed breather, which worked flawlessly, and a Ducati reed valve breather, which also worked flawlessly. However, I check my valves and ring leakage quite a bit with the much loathed leak-down tester.

David
 

stumpy lord

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Interesting points made so far.....can anyone relate to this....Series B type UFM with the normal oil filler cap complete with vent hole clear and unobstructed. Initially ran with the chain oiler pipe fitting at rear of UFM blanked off. At speeds over 80 mph on the highway, would cause oil to spew out of cap area and all over the fuel tank. I then opened the blanked off fitting and plumbed it just above the swing arm pivot area with a T fitting into the existing D type beather cap outlet line using a larger bore fuel/oil hose and ran to the rear next to the axle, this fixed the oil over fuel tank problem, and the pipe at the rear only drips the odd drop of milky oil after a descent run. The oil tank is only filled to just above the steel bridge plate, visable down the filler neck. The reason this all came about was due to the chain being over oiled in the first place.............Cheers......Greg.

Sounds as tho you were suffering from the well known two start pump problem i.e. a heavy return of oil and air splashing up on to the bottom of the oil cap, and being forced out of the breather hole by the excess of air being delivered to the oil tank by the oil pump [don't fore get that the oil pump delivers more air than oil to the tank] Most two start pump users get over the problem by fitting a small piece of stainless steel in side the neck of the oil filer neck held in place by the chain oil adjusting screw screw to direct the oil flow downwards into the tank and away from the cap.

I must admit to never having seen inside a series B oil tank, but I doubt that the second pipe you are talking about is a breather pipe. but rather a pipe for oiling the rear chain. I may of course be wrong, but do not see why the breathing of the fuel tank is O.K. with a small hole in the cap, and it is not sufficient for the oil tank. could it not be that the works found that an unobstructed feed to the chain caused a great many problems with over oiling, we all know how much oil can be blown out of the oil tank breather hole when having over filled the oil tank, can you imagine what it would be like on your rear tyre. consequently the outlet into the tank was modified to give some sort of control over the feed to the rear chain , unfortunately, as I said before, due to the pump running at different speeds and the oil getting thinner as it gets hot, it is just about impossible to adjust. that being the reason why most owners screw the adjusting screw down, and blank of the outlet

I am open to correction.
stumpy lord
 

greg brillus

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Hi all, Well as far as i know the engine has it's standard pump and is probably one of the first die cast engines the factory made. I think if the engine was any more standard it would run on kerosine..... I was of the oppinion that the chain oiler was also a tank breather, but from what you say this is not the case, which proves the importance of the vent hole in the cap..........Greg.
 

davidd

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Like Stumpy, I would never run a chain oiler (other that a Scott oiler.) Richardson does refer to the B chain oiler as a "vent", so Phelps is correct. As someone who installed a vent in my UFM at the highest point, with an angle and a small filter, I will say that oil poured out of it at high revs. I do not put much oil in the racer because it uses none and a small quantity of oil will heat up faster. All I can say is that there is an "oilnado" going on inside the tank. We think of the bike at idle spitting up a little oil, but at the higher revs I can only assume that it is shooting out at an impressive rate. Many racers have told me about the oil vent spewing on their face shield at speed in a full tuck. This has happened to me also. It is why I put a deflector in the top of the oil spout. The more you can keep the mixture of oil and air away from the cap, the better off your are. This deflector works on the C UFM:



David
 

BigEd

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Part # T29 on drawing MO18 is listed as "Tank Breather Adapter" so I guess that it was intended to be a breather at some stage of Vincent development.

I must admit to never having seen inside a series B oil tank, but I doubt that the second pipe you are talking about is a breather pipe.
I am open to correction.
stumpy lord
 

ogrilp400

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The second pipe resides along side the oil return. It has a closed top with a small hole in the side. This pipe leads down and to the rear of the tank where a fitting has a steel tube hanging off it. If the oil level in the tank is quite high then this pipe will issue oil.

"I must admit to never having seen inside a series B oil tank, but I doubt that the second pipe you are talking about is a breather pipe.
I am open to correction."
 
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