E: Engine Breather Timing: A long description of a different way (Part 1)

bmetcalf

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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

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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

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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

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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

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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

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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

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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

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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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