engine breather

I placed my xs reed breather in place of my combat rear of crankcase stock breather, but I have to ask if there is any advantage to positioning it on the timing chest or weather having two, one in each position would be counter productive, I'm curious,

Although close to the case is advantageous to effectiveness, it has always been my thinking that the 72 crankcase will send oil out that lower left orifice. Oil passing through the reed may cause pressure and defeating the purpose to some extent. I bet Jim Schmidt could tell you how hard it is to play a saxophone with a mouth full of 50w. Mounting it up higher and tubing it across to the tank seems to work better, at least in my mind.

Mounting at the timing case is common and the breather of 850's are there already. Some believe too much oil in the timing case robs some power and seal the hole that allow the crankcase to breath through it. Again, theory.

I run two breathers as you suggest. Both are totally audible in their function and operate in unison. I feel in this particular instance that it supports the old adage, "If one is good, 2 is better". The way I see it, it sure can't hurt.

I run her kinda hard and it stay pretty clean with little to no oil blowing out.

For what it is worth, I say the main breather is on the crankcase running to the oil tank and the secondary breather coming from the TS dump to the atmosphere. I thought of connecting them together at a "Y", but that WOULD be self-defeating.

I have it low on my 72. Any oil pushed past the valve is quickly moved to the oil tank. Even can help if you are wet sumped.

Leave it low and run it to your oil tank.

No need for two of them.

[video]https://youtu.be/Ti9PvFfsfm0[/video]

Wouldn´t it be helpful to have a breather from the head as well? You see this on practically every car engine, just thinking the pulses have to go up there too, or are the pushrod channels too narrow to let anything past? Interfering with the oil transport.... :? . Well it´s early sat morning, an old man trying hard to wake up, the mind roams free :roll:
Tommy

fiatfan said:

Wouldn´t it be helpful to have a breather from the head as well? You see this on practically every car engine, just thinking the pulses have to go up there too, or are the pushrod channels too narrow to let anything past? Interfering with the oil transport.... :? . Well it´s early sat morning, an old man trying hard to wake up, the mind roams free :roll:
Tommy

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Keep in mind that practically every car engine is wet sump whereas the Norton is a dry sump; this difference may make a difference in engine crankcase breathing strategy.

Interesting point you make about pushrods channels. Many Norton race engines have a direct drain plumbed in between the intake valve spring pockets. This is usually done due to the factory oil drain drilling from that area being encroached on (and subsequently plugged) by wider ports.

The point is that the pressure is created in the crank case. So, that's the most logical place to vent it.

With a reed valve in / on / close to the sump, you simply do not need anything plumbed into the head.

I have Jim Comstock's sump plug reed valve breather and am very impressed with it. The overall reduction in gases passing back and forth at the oil tank breather outlet is really quite surprising.

A friend who in his more youthful days won championships racing Commandos and who now repairs and prepares peoples road and race motors once said to me of that so callled breather at the rear of the conbat cases...the **** thing pumps more oil back to the tank than does the oil pump. It was as 'clever' as Triumph removing the crank oil seal and breathing into the chain case (only done on production bikes to ensure the correct oil level in the chain case as so many bikes being serviced at the factory were found to have dry rustry damn nigh solid primary chains due to ownber incompetence...so a Triumph Service Manager told me and I believed him). On the BSA unit B50 they were even more 'clever' they removed the oil seal allowing the motor to breath into the chain case...kept the original rimed breather system and FORGOT to put some drain holes back into the crank case to limit the oil level in the chain case thus ensuring clutch slip became an even greater problem!! Another Slumberglade Hall total cock up!!
Clearly a BIG pile of these Combat cases were quickly hidden away in the factory because after NVT went to the wall in the cellers of MCE in Birmingham there was a BIG pile of them available for £20 a set which no one seemed very interested in buying.(New RH6S boxed 750 heads were £40 each!!). Apart from buying a couple of new heads I bought a couple of sets of crankcases and modified them by ..
1 Blanking off that so called breather.
2 Replacing the original drain plug / guaze filter so oil passes through it BEFORE bits of piston ring etc make their way back into the pump.
3 Shoved a BMW reed valve breather where the magneto had once been.
4 Installed the cam shaft oil bath that rthe idiots had forgotton all about ...enabling the cam was to be correctly lubricated and not to fail prematurely......
In use the reed valve could be heard working for the first few rpm but after that only very occasionally because unless you have piston rings not sealing correctly crankcase pressure settles down to a nice low value.
If memory is correct on Triumph twins a very simple breather system once used that testing showed gave a crank case pressure of around 1 lb was as follows......the breather pipe was taken back to the oil tank....the oil tank screw filler cap had a tiny hole drilled in it......upon engine start up the crankcase pressure pressurised the tank but some of it was blown out the small hole.....as the pistons went up hardly any air was drawn back into the tank through the small hole.....after a few revs crankcase pressure settled down to a nice low pressure. I believe Mr Oswald of QPD in the USA recommends his Triumph and BSA dry primary belt users adopt this system, probably because it requires very little skill to incorporate!!

Incidentally the reason some people have for many decades run an extra cylinder head drain back from between the inlet tracts back to the crank cases is because the existing drain from the inlet side via the head and barrel is not sufficient when employing the double rate oil pump gears and the oil builds up in the head covering the valve guides and eventually it is so high it flows over into the exhaust side. To stop every Commando laying down a smoke screen like an Ariel Arrow or a destroyer protecting a convoy Norton shoved seals on the inlet guides......clearly some people think oil seals on inlet guides not a good idea.......I suspect they were simply a bodge as doing the job correctly would of cost money to incorporate.

I´ve read numerous posts on this subject, and I naturally understand that when the pistons go down there will be a certain pressure developed and this is then vented out through the reed valve (if you have one). But in my engine the pistons also go up from time to time, and every time they do the reed valve closes? So where does the air that must fill the crank case when the pistons go up come from? :? I think I have to give Steven Hawking a call.... :lol: :lol:
Tommy

fiatfan said:

I´ve read numerous posts on this subject, and I naturally understand that when the pistons go down there will be a certain pressure developed and this is then vented out through the reed valve (if you have one). But in my engine the pistons also go up from time to time, and every time they do the reed valve closes? So where does the air that must fill the crank case when the pistons go up come from?

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It is drawn from the head and timing chest, creating a very slight vacuum.

THAT is why the oil leaks stop.

Mr Leadbeater,
You talk about the camshaft oil bath a lot!
And I'm not disagreeing with you on the matter.
I just would like to know what you (or anyone else) thinks is the best method for re-creating this in crank cases where it is not?

Weld in 2 shelves.