A: Oil Pipework Breather back into oil tank

vincenttwin

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Any one running a engine breather back into the oil tank by way of the chain Oiler , if you have do you have the details of the fittings used on the oil tank and did you just open the screw adjuster open or did you remove it .

I ask only replay if you did this and know the details
Thanks
 

Gary Gittleson

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I did something like this with a goal possibly opposite to yours. I have a D Rapide, so there are likely some other differences. My goal was to stop the breather on the oil tank from spewing small amounts of oil. Since my bike is a D, it has no timed breather. It does have one of those D-style caps on the front cylinder. I mounted that over the front intake valve (instead of over the exhaust, so it can't be easily seen). I then added a one-way valve to the attached hose and routed that to the rear of the bike.

Next, I drilled an old valve cap and threaded it for 1/8" pipe thread (NPT). I cut one threaded end off a brass 1/8" pipe nipple and bored that end to fit a bit of plain brass tubing whose OD was the same as the fittings on the oil tank (5/16"? I don't remember). That was then soldered in place and the remaining threaded end of the pipe screwed into the valve cap. The cap was installed over the rear exhaust valve. I installed a hose from this new breather to the chain oiler fitting on the tank and removed the metering screw. The screw was replaced with another one with no point which holds a deflector I made for the return oil. I also bought a non-breathing oil tank cap. The whole thing seems to be working quite well. I still see a small spot of oil (an inch or so) on the ground after a 100 mile ride, coming from somewhere under the right side of the engine. I plan to put the bike on a lift to search for the source.
 

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stu spalding

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An article on this subject was written up in MPH 571, Aug '96. Ray is right to point out that the hole in the oil tank filler cap is for oil tank breathing only. Cheers, Stu.
 

Little Honda

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Ernst Hegeler of Varel, Germany (VincentSparesGermany) adds to all his oiltanks a breather pipe which works
inside by impact separation oil from air, plus velocity reduction when leaving the pipe inside. There is also a
surplus pipe exit to a breath collector, size like a small beer can, hidden somewhere suitable.
His engines are dry. At touring speeds, no oil enters the collector.
I do not know, if he converts customer´s oiltanks.
 

davidd

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Little Honda is correct that there needs to be a separator inside the ufm if you are piping anything into it. The oil permeates the atmosphere inside the ufm and it will find its way out if you give it one.

In general, I don't think there is anything wrong with using the chain oiler tube, but it is probably too small to deal with the volume of blowby that most Vincent owners seem to run with.

If I remember correctly, the screw adjuster is a red herring. There is an equal size hole drilled into the block of the adjuster on the timing side that is barely visible. This is the breather hole that was designed to work on the Series B chain oiler with no adjuster. When the adjuster on a C is wide open, the oil will simply flow out this breather hole into the tank. I think this was done to prevent the chain oiler oil line from being pressurized. The chain oil hole takes whatever it can from the oil passing by on its way back to the tank. The adjuster screw simply lets more oil flow by the hole. Thus, closing the adjuster screw minimizes the oil going by the chain oiler hole, but it does not close it. The oil can come in through the timing side hole in the adjuster block just like it did in Series B's.

You can try this out by putting a plastic hose on the chain oiler end and blowing through it with the oil adjuster screw fully tightened. You will find no resistance as the air is flowing out the timing side hole.

Chain Oiler Description.PNG


David
 

stu spalding

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Thanks for that David, when I did the mod in '96 I didn't realise there was a "spare" hole in the block. Cheers, Stu.
 

Little Honda

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Regarding Davidd´s note, that the chain oiler´s tube is too small in diameter for the blowby volume, I would like
to put your attention on the rocker bearing, where the majority of air volume has to pass opposite to oil flow
downwards through the tiny oil channels at its bottom. This area is even smaller than the chain oiler tube thus
resulting in higher air speeds against oil flow direction.
Consequently, any breathing from the top of the valve springs is located at the wrong place, as the highly
accelerated air speed at the rocker bearings will enlarge the oil content in the blowby.
Therefor, any blowby should be conducted from top of the inspection caps over the valve clearance adjustment screws, where air speed is much slower to avoid any hinderance to the oilflow down the rocker channels.
Anybody should note, that non-return valves, no matter, what kind of, do have their individual limit where they
remain open. Therefor, it makes sense - as adviced by PEI in TFS - not to use too large a diameter of breathing
tube, to use the inner resistance of the breather tube to restrict air volume entering the oil tank. He recommended an inner dia. of app. 1/4" for a twin engine in good nick. For normal road use, it might be
sufficient, to run yr blowby return line even without non-return valve, which makes no sense at all on a race
engine.
 

davidd

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I would have liked to shown Phil Irving the breather on my racer. I have never had a catch can on the bike and it has been ten years. There isn't even oil mist around the outlet, which is hidden under the tank cover. I don't know why it has worked this well, but considering it has worked on several engines I might guess that it has something to do with getting the rings bedded in and running the engine with little or no blow by. I would do a leak down test every racing weekend.
PICT0007.jpg

Right above the carb is the Ducati reed valve breather with a wash cloth zip tied around it so it didn't bang around. I also zip tied it to the carb. I never replaced the cloth and there was never any oil on the carb or the exhaust. The tube runs from the generator hole.

I do think that blow by is a bigger problem at low speeds than high speeds. It could be that the peak power being at 6900 rpms makes a difference. I could not go below 4200 rpm due to EGR. It would idle, but there was no power. Slipped the clutch to 6000 to get off the line and was often first in the corner (unlikely to be first out of the corner!)

David
 
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