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E: Engine Breather Timing a long description of a different way. (part 1)


Nigel Spaxman

Well Known and Active Website User
VOC Member
At first I wrote this with the idea of MPH, but then I though why waste all that paper, I might as well just post it on here. I am glad you are all enjoying this. Maybe it will eventually be in MPH. I think it might reach a lot of other people by being in MPH. I would love to know what Neville Higgins thinks of this.
 

Nigel Spaxman

Well Known and Active Website User
VOC Member
What I would love to see is a Vincent with a dry back tire after a 300 mile ride on a hot day.

They all seem to put a little oil on the tire.
My 1360 is promising, but I haven't done a 300 mile summer day with it yet.
On a long group ride some years ago a friend who was new to Vincents commented on this. " Every bike here has some oil on the back tire " was his comment.
There were about ten twins plus a Comet present.
I had a good look around and he was correct.

Maybe a catch bottle is the only way to eliminate this. A better breather will only add a bit more mist to the rear tire problem.



Glen
That's why a lot of people run a hose way out the back with a nozzle pointing outwards. On a perfect engine I think mist comes out of the breather pipe.
 

oexing

Well Known and Active Website User
VOC Member
On a good engine there will be next to no oil mist from the breather - provided it is a one way reed or ball type. I will definitely fit a breather hose to the front or rear inlet valve cap with the reed valve at the highest place of the tube so any bit of oil collecting there will run back into the engine. With a one way valve there is very little air coming from the crank case.

Vic
 

vibrac

Well Known and Active Website User
VOC Member
Do you realise that this subject has been talked about on the Forum for 10 years! if you don't believe me put "breather" in the search box top right
Not only that there are 50 years of MPH articles before that some suggesting altered timing of the valve.
It must be the most talked about subject in the VOC club, funny thing is its rarely mentioned on other makes
 

Glenliman

Well Known and Active Website User
VOC Member
I don't think there is a breather hose termination (other than a catch bottle) that will prevent the mist from getting on the tire.
As mentioned, there were 11 Vincents that had just completed a good run and all had the dreaded moist back tire. Two or three might have had tired engines, but the others were all in good shape. I'm not sure if any had reed valve arrangements.

My OZ bike has the Eddie Stevens well back and curved out twin SS pipe breather termination. This is designed to eliminate the oil on tire problem.
The SS tubes and mount look very nice, but there is still a little oil mist getting on the tire.

When all of the leaks are plugged, this bike uses very little oil.
At the end of a 2500 mile trip to California it required just 8oz to bring the level back up.

Glen
 

oexing

Well Known and Active Website User
VOC Member
Sorry, I should have been more specific: Timed breathers are quite OK as well when timed in a proper way. BUT: The original plus the elephant trunk get oil loaded air from the timing chest without much of a chance for the oil to separate from air. It is just not a brilliant place to fit a breather. So that is why I will pick the valve covers for adding a hose plus reed valve - and the reed valve at max distance from the cap so oil mist can settle and return into the engine. Works that way great on the 460 cc Horex that had a timed breather from the primary sprocket right vertical to the bottom - and a drop of oil regularly. So a reed valve went into the big valve cover in a box with ss wool as mist filter.

Vic
 
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Glenliman

Well Known and Active Website User
VOC Member
Do you realise that this subject has been talked about on the Forum for 10 years! if you don't believe me put "breather" in the search box top right
Not only that there are 50 years of MPH articles before that some suggesting altered timing of the valve.
It must be the most talked about subject in the VOC club, funny thing is its rarely mentioned on other makes
That's because they are oily old buggers.
At the final Vincent Owners Club presentation for the IOM event in 2007 there were at least 150 Vincents parked on a rather nice flagstone patio area.
When it was over the flagstone looked as though the Exxon Valdez had gone aground there and split in two!
Still lots to talk about when it comes to Vincents and oil leaks.
Many have given up, some are still fighting the good fight!

Glen
 
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Glenliman

Well Known and Active Website User
VOC Member
Just remembered that when John McDougall rebuilt the top ends on my OZ bike he worked his way into the timing chest as well.
Good thing, there were some issues at play in there.
One of the problems was with the breather.

I recall being quite thrilled with the bike first season as it did not drip condensate goop from the breather like all of the other Vincents. I took this as a sign that the engine was in great shape.
John found out why there wasn't anything coming out of the breather pipe.
The breather sleeve was seized on the spindle and the pinion was rotating on the sleeve!

Anyway, I see in the notes he provided which list labour performed each day"
"Opened up breather"
Now I recall discussion of this, but of course at the time I had no idea what he was talking about.
He definitely had his own ideas about breather timing and also modifying the breather for more open time.

Glen
 
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oexing

Well Known and Active Website User
VOC Member
Yeah, another reason why I did not keep the original timed breather: The "alu bush" inside is not a real great bearing with its slot. Instead a needle bearing went in there and a reed valve will be connected to a valve cap.

Vic
 

Glenliman

Well Known and Active Website User
VOC Member
On the other hand the replacement breather has done 55,000 miles without complaint
At least I think it's ok, haven't peeked inside there for 55,000 miles.
A few drops of grey goop still show up on shutdown, so I think we're ok:)
 

bmetcalf

Well Known and Active Website User
VOC Member
Nigel, in post #2, you recommend "set the opening of the valve at about 90 degrees ATDC and the closing ended up at about 50 ABDC". Is this for motors with the spindle slot pointing forwards or for pointing down, like your motor? I assume the former, but please advise.
 

timetraveller

Well Known and Active Website User
VOC Member
Errr, I think that the opening/closing of the breather valve is a function of both the slot position in the spindle and the opening in the breather tube with the pinion. Rotate one and you have to rotate the other. To me the angular position of the slot in the spindle is more to do with whether one is trying to prevent oil passing into the breather outlet. Given a combination of slot positions in both items then they can be timed to open or close at any required engine rotation value.
 

Nigel Spaxman

Well Known and Active Website User
VOC Member
The timing is set by blowing in a hose so the direction of the slot is taken into account. The angle of opening is the angle you read on a timing disk when the valve opens and closes (not the actual angle from vertical of the slot in the gear) I put my slot facing down because I missed the instructions about having it set pointing forwards. Down seemed the obvious way to me. The reason I set it pointing straight down was to promote the maximum drain back of oil through the valve. The factories idea was to have the slot pointing away from sources of oil to prevent oil being carried out with the air, that might be better, I would do it that way if I do it again. I doubt it makes much difference though as long as the slot is not pointed either up or straight back which probably would increase the amount of oil going out the breather. I think that if you really wanted to minimize the amount of oil going out of the timed breather the best thing would be to have a fairly large diameter breather pipe going straight up the front of the engine and then a smaller hose to the back of the bike. I didn't bother doing that because I think it would be ugly.
 

druridge

Well Known and Active Website User
VOC Member
Not to disagree with what's been said above.... but.....
My bike discharges from an out-turned pipe near the rear of the RFM as Stevens in KTB. If the pipes not turned out properly I get a bit of oil on the side of the tyre after a decent run, otherwise I get a few drips on the garage floor when I park up. After working for BP for a number of years I refer to this stuff on the floor as 'mousse'. Its the cafe creme coloured stuff that's a combination of oil, air, and water. Always all three.
I know where the oil comes from, after reading the above, we all know a little more about where the air comes from. Unless we are in major trouble, the water is condensation.
This 'mousse' is not good stuff to have in an engine, and can be a serious problem in the wrong place (imagine pumping that through a set of plain big-end shells). It doesn't flow as oil, and is unwilling to settle out, once frothed up,for practicable purposes, it stays as mousse . I'm not exactly sure where in our 'discharge systems' the water component becomes significant in the already present oil and air, but as our engines arn't usually filled up with that gloop, its clearly quite a way through the system. A reasonable guess might be actually within the external pipework where its being cooled?
I've come across this mousse in reasonable amounts in round barrel Guzzis (T3/ Le Mans 1), where it is collected in a breather box. On the Guzzis, the engine breaths from the crankcase, gearbox, and the 2 rocker covers; all via external pipes into a tin box about the size of a fag packet. The box contains a ball valve and separator/spill where oil is allowed to dribble back, and a vent to air. On flushing these boxes out they are often found to be full of mousse on apparently healthy motors. Within the motors themselves, I have only ever found the smallest amount of mousse right where the breather hoses join the rocker box covers.
One function of any system of valves, balls, flaps etc needs to be to ensure any mousse stays on the correct side, that's the side away from the motor - and that there is no way back. On plenty of bikes gravity works really well.
 

oexing

Well Known and Active Website User
VOC Member
I´d say get yourself a twostroke . You are doing too many short trips ! The engine never gets hot enough long enough to boil off the water from cold starts. A minimum of half an hour drive should be the plan.

Vic
 

Bill Thomas

Well Known and Active Website User
VOC Member
To me , If you have a pipe going downwards, Even if you have mist, It will turn back to oil, and run down the inside of the pipe.
That's why I would not have a standard breather.
I use a car oil separator, Mounted high, With a short level outlet, And my Engines are race spec, A bit worn out !. Cheers Bill.
 

Gerry Clarke

Active Website User
VOC Member
Respectfully, having held the crankpin in your hand as a measure of true ownership, does not admit those who have covered in excess of 100,000 miles without having to so do.

The design intent of the original breather system was conceived in tandem with the rest of the bicycle being in reasonable condition. From my own experience, the bog standard system works just fine at road legal speeds.

And finally, again with respect and as a design engineer long in the tooth, may I reprise my beloved grandmother's wisdom and offer that "self praise is no recommendation".

Gerry
 

greg brillus

Well Known and Active Website User
VOC Member
Most all Vincent's are fine up to about 65 to 70 MPH beyond that they will start shedding oil from somewhere if you hold these speeds for any descent duration. The factory breather is ridiculously small for such a large capacity engine. This is why the Elephants trunk set up works so well, but like a third exhaust pipe, it looks ugly. Having said that, when in good condition the engine breather does not tend to loose large amounts of oil, and it is unrealistic for any older machines to not loose oil, the older the machine the worse the problem usually. I found the people who struggle with this are folk who drive or ride modern machinery who have either never had an older machine, and are use to vehicles that never drip a drop no matter how hard you push them............They need to get over themselves.
 

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