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A: Oil Pipework Breather back into oil tank


vincenttwin

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VOC Member
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
 

vibrac

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I hear what little honda says about venting from caps over valves but practical experience on the egli big bore where we had front exaust and rear inlet caps routed upwards to one way valves and down to a manditory 500cc catch tank which resulted in a spoonfull of R after a seasons racing leads me to endorse what many say engine condition is all.....
..
27586
 

Little Honda

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David,
I always wondered, why Vincent twins are so very different from singles. Even Ernst´s short
stroke engine, which reaches 8000 rpm, shows very little sweat over a race weekend. The normal Comet racer
also does not collect any blow by in its bottle over a season.
His Lightning is relatively dry for a twin, ie, over a race weekend, it collects about 0,1l of mud in the collector,
but no oil. If there are long straights on track, she shows some mist here and there.
My Norvin (no race use) is so different: On a weekend trip over some 500 miles of riding, it is visibly oily and
drops, whereever parked, after arrival.
Ok, a motorway trip is a much longer time period of running to let the engine collect blow-by and add up
internal pressure, compared to a 15 - 30min race. In this point, blow-by seems to be an additive effect,
which remains non-critical at short time intervals.
You may be right, stating that blow-by is more at low speeds, say up to 1500 rpm. This is about the limit, until
timed breathing is effectiv. After this, you will need sufficient atmospheric breathing (as Honda uses everywhere) But, that is not the point: If it is right, when an engine is less gas tight at cold temperatures, than
at operating temperatures, this must be seen per working stroke, which means, that every single blow by volume adds to a total in your crankcase, depending on revs. Even , if your engine is more gas tight at higher
revs, it will add to a higher total pressure in your crank case due to double revs.
My impression is, however, that bow-by is worse at high revs at high engine temperatures, which is easier to understand, when thinking about how a piston ring works. His tightening abilities are more difficult at high
speeds, the more in the aspect, that the tightening force is mainly done by gas pressure from behind the ring.
The only reason, why a twin engine does leak more than a single, is - to my impression - that, per cyl.-volume,
the relating crankcase volume on a twin is smaller, than on a single. This could easily be measured, like bakers measure bread volume: by pouring poppy seed into a glas cylinder, in which lays the bread to be
measured.
This could also be done on any engine, but it must be dead dry inside, to get out again 100% of the poppy
seed to measure its volume.
Good, that at present times, bikes with "patina" are valued higher, than gleaming dream bikes, which I
could never afford....
 

Bill Thomas

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Why don't we hear more from Germany, Are they Modest !!, The web site you showed us the other day has a lot of nice stuff, If a lot of money !!.
Cheers Bill.
 

Little Honda

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VOC Member
Bill,
are you from Scotland? Regarding prices, you should note, that the Hegeler generator comes with regulator,
plus complete electronic ignition, all included, except plugs. Ernst never learnt English language in his lifetime,
so that is why there is not so much communication in this place.
I do that for him, when needed.
You can meet man and machine at the Caferacer Festival, this coming weekend. There you can see his Norvin
with his own engine in operation.
cheers, Little HOnda
 

Bill Thomas

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No welsh, just old and poor, l remember the old days, when this stuff was cheap.
Still think the d distributor is the way to go. + a Walkernator.
Cheers bill
 
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timetraveller

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I had a brief ride on the Hegeler 'Norvin' about three years ago at the Pioneer Run meeting near Dick Sherwin's. Although I only covered about four miles it was clearly a very nicely handling bike with a very useful electric start system. Ernst is a talented machinist and designer but does not like to fit his starter system to existing bikes as it means machining the original drive side crank case to get it to fit around the large starter gear.
 

davidd

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VOC Member
I wish I knew more about breathers. Frankly, when something works for me I don't pay it much attention any longer. I think that I said "blowby is worse at low speeds" but I should have said "windage is worse at low speeds."

David
 

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Little Honda

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Agreed, David. "Never touch a running system" is the saying. I discussed the problem of breathing twins with
Ernst today on the phone. His opinion was similar to your added article. So I suggested - to check, if the crankcase volume in Vincent twins is so much smaller, than on singles - simply to add a temporary tank volume
in the size of the standard crankcase volume, thus doubling it. This should show, if the twin engine under these
conditions would behave like a Comet. If not, some more thinking has to be done...
ps: this tank having no atmospheric exit, of course
 

Bill Thomas

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All you need is a big hole up high, With an oil separator, No catch tank !, My engines are race type and worn out, Like Me !. Cheers Bill.
 

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hrdaustria

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VOC Member
All you need is a big hole up high, With an oil separator, No catch tank !, My engines are race type and worn out, Like Me !. Cheers Bill.
good morning,
we are testing our recently finished three breather prototypes on a rapide, a comet and my shadow. the main focus was to lead the pipe downwards on the breather outlet as its mostly hided by the exhaust on twins. some of you have seen my shadow at the international, a dry bike. we´ve not yet found any oil leaving the breather pipe. no reed valve is used.
michi
 

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