Author Topic: Engine breathing (Oil drip)  (Read 10850 times)

Online Brian

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Engine breathing (Oil drip)
« on: 03.12. 2007 00:48 »
I was wondering if anyone has modified their engine breathers and what they have done. I know some put on a inlet rocker cover with a vent hose. The problem I would like to overcome is when you pull up after a ride there is always a drop of oil on the ground from the breather tube. What I had in mind was to run the breather tube into the primary case and vent the primary case to atmosphere. I like to try and get my bikes totally oil tight and this has been annoying me for quite some time, any ideas?    Brian.

Offline a10gf

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Re: Engine breathing
« Reply #1 on: 03.12. 2007 01:59 »
Here it is! A container with a pipe from the breather, a small fueltap at the bottom, emptied when nobody is there to watch :O)


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Online Brian

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Re: Engine breathing
« Reply #2 on: 03.12. 2007 03:37 »
Thats a good idea and is what I will do for now while I think about it. At this stage I am still considering the into the primary case option.

Offline LJ.

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Re: Engine breathing
« Reply #3 on: 03.12. 2007 09:15 »

I had only recently fitted a breather tube from the crankcase as I could feel quite a strong breathing there while the engine was running and I was suspicious that alot of oily mist was covering the underside and behind the primary. Since fitting the tube, although quite dry, it still breaths quite forcibly. I'm wondering if there should be an odd drop of oil from the tube after switch off, or do I have a very well set up breathing system? It seems that BSA didn't put in any hose as such and just alllowed the engine to breathe straight out the side. Could your problem Brian, be the thickness of the oil??

I dont think rocker inspection covers with breathers are a good idea or draining into the primary. I'm sure that BSA would have done that if there was any real benefit.
Ride Safely Lads! LJ.
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1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
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Online groily

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Re: Engine breathing
« Reply #4 on: 03.12. 2007 10:01 »
I note on my engine someone has attempted the rocker cover breather mod - and then blanked it off. I assume because it turned out not to work, to leak, or whatever. Certainly it's not the ideal place. I think a collector system is probably best, as what comes out is actually supposed to, within reason, and pressurising other places can't really help much and maybe could make more leaks? Groily
Bill

Online Brian

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Re: Engine breathing
« Reply #5 on: 03.12. 2007 11:04 »
Going by the picture in the parts manual the original breather tube BSA fitted appears to have gone straight back to the sprocket, possibly so the odd drip went onto the chain. This is not a big problem but I dont like the odd drip, especially when I pull up on someones new driveway and tell them how british bikes can be oiltight !!!

Offline a10gf

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Re: Engine breathing
« Reply #6 on: 03.12. 2007 13:00 »
Out from the shop in 1955 or whatever date they were oiltight ! I see on my bike (and others) the leaks were bad gaskets, uneven tightening of screws, and deterioration of contact surfaces (f.ex somebody in the past enjoyed splitting the crankcase with a screwdriver + hammer etc). I had some damaged surfaces built up again with auminium welding and then I filed\polished to get the original contact back, = 99% oiltight with an ok gasket. The very small emanations I've got is no more than can be wiped away now and then or when cleaning the bike.

The breather is another story, on my bike there is quite a lot oil\condesation mix coming out, due to all kinds of yet unknown reasons, but the little container fixes it in practice. If you fit some oil-container, remember to have some top hole on it to let any pressure out. btw I enjoy parking next to other british bikes (look, no oil drips ! ).

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Re: Engine breathing
« Reply #7 on: 03.12. 2007 15:46 »
If I am following correctly, the little oil container is for catching drips coming from the oil tank vent. Is this correct? Apparently, the issue raised by LJ regarding mist from the crankase breather collecting behind the primary is not helped by the drip collector. The recent disassembly of my engine was done after very few miles, but the mess behind the primary was significant. Perhaps this was due to other problems that led to the disassembly, however, if that was normal for such low mileage, I want to consider a fix. Has anywone tried something like tapping the breather port and installing a fitting and tube to route the mist down to the street rather than spraying it on the crankcase? 

Richard
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Offline a10gf

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Re: Engine breathing
« Reply #8 on: 03.12. 2007 16:06 »
Quote
If I am following correctly, the little oil container is for catching drips coming from the oil tank vent

There should be no possibility for spill or pressure from the oil tank vent. It's the engine breather. My theory, with an engine in perfect condition everywhere, the oil amount from the breather will be very low. As wear escalates, the crank pressurising from valve guides, cylinders and things I have not thought about, may force more oil out the breather.

So rather than doing the whole engine prematurely because of some oildrops, it's collected with a tube from breather to container. Emptied now and then, quite a lot in there sometimes, water(condensation)\oil mix.

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Online RichardL

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Re: Engine breathing
« Reply #9 on: 03.12. 2007 17:31 »
Erling, et al,

I think I know why I am confused. The breather path on earlier A10's, like on the plunger (I think) is different from that used later, where the outlet path passes under the camshaft oil gallery and exits behind the primary case. (I learned this during a previous thread where we were discussing the "unusual" cam pinion gear.) Am I correct that that is not the path used for your bike and that the breather output is somewhere toward the right side rather than the left?  If so, by what means is the tube to the trap connected to the breather output?

Richard
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Offline a10gf

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Re: Engine breathing
« Reply #10 on: 03.12. 2007 20:51 »
Hi Richard. On the plunger the breather pipe exits near the rearchain gear sprocket, which is the left hand side of the engine. Suppose it's meant to drip on the chain. There is a piece of plastic tubing that fit a protrubing breather outpout pipe, routed to the extra oil container. Not my idea all this, it was like this when I got the bike, found out it was worth keeping.

E.

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Offline LJ.

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Re: Engine breathing (Oil drip)
« Reply #11 on: 03.12. 2007 22:13 »
Ah! It's off to the parts book to see if I have always been missing a breather output tube on the swing-arm.

I could not see any mention of one in my books... There was nothing on my crankcase. (1961 Swingarm)
all there was was a hole.... I put in a nice fitting brass tube with a rubber hose led down to the bottom of frame.
Ride Safely Lads! LJ.
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1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline a10gf

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Re: Engine breathing (Oil drip)
« Reply #12 on: 03.12. 2007 23:08 »
In the 49 to 53 engine chart the breather pipe is there, pnr. 67-922.
Is it not supposed to be there on later models? Maybe dislodged by a loose chain or something ?

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Online Brian

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Re: Engine breathing (Oil drip)
« Reply #13 on: 04.12. 2007 01:09 »
The swingarm models do have a tube, same part no as the plunger models. They are a press fit in the case but I always put a drop of loctite on them as well. In my experience with A10's they seem to pump a bit of oil out when you first put the motor together but after about 1000 miles it settles down to just the odd drop which is what I am trying to overcome. I have decided to put a catch bottle on for now and in the future will either run into the primary case or back to the oil tank. At least we have created some discussion for the Forum which is always good.        Brian.

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Re: Engine breathing (Oil drip)
« Reply #14 on: 04.12. 2007 01:56 »
I would not recycle the expelled oil, can contain condensation \ water.

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