Breather mod. - all engines | Norton Owners Club

Forums

As there are frequent messages on this site regarding breatherproblems and modifications I would like to suggestanother one.

There are numerous variations, but the sole purpose of any breather is to vent excess internal gas pressure in an engineand if at all possible leave a partial vacuum.

Nortons have mainly used a mechanically driven disc valve with varying success. However Royal Enfield simply chose to use a rubber one way valve. Yes, Royal Enfields are not famous for their oil tightness but this was due mainly to their construction of independant barrels and poor head sealing. However the rubber "DUCK BILL" valve isVERY effective at maintaining a partial vacuum by simply blowing off excess pressure and sealing immediately when the pressure declined and not allowing air back into the engine. They look just like a rubber pipe so are completely unobtrusive and will go unnoticed on any bike.

These are still readily available from Hitchcocks Motorcyles and are quite inexpensive at £1.65. They can be added to the end ofany breather pipe to add an extra one way valve property. When the rubber pipe of the valve is slightly warm and softened,the effective action can be seen to work, especially at tickover speeds, as the pipe/valve puckers up showing the valve is indeed creating a strong vacuum. If a strong crankcase vaccuum is created, there should be a reduction in the amount of oil blowing out of the breather and a reduction of engine oil leaks.

Hope someone getsa benefit with this.

Les H

Hi Les interested in this…

Hi Les interested in this valve but unable to locate this on website unless it is a flat ended pipe? sorry to be trouble again. eddie

My Domi has the later oil…

My Domi has the later oil tank. The engine breather goes to the tank and the tank breather goes to the rear chaincase. That way the rear chain gets some oil mist once the engine is nice and hot and also, if the bike has been standing for weeks, any oil pumped out of the breather goes to the oil tank.

I had a 250 Enfield with the one-way disc breather. Fine up to 50 mph but then the leaks started...

Still, I like the idea of the one-way valve. Might try it on my (shock, horror) BSA.

Hi Eddie and Gordon. The v…

Hi Eddie and Gordon. The valve is the flat ended rubber tube. You can see them on Ebay but Hitchcocks has them (plus VAT and postage too)

http://motors-parts.shop.ebay.co.uk/Motorcycle-Parts-Accessories-/14780/i.html?_nkw=duckbill&_catref=1&_fln=1&_trksid=p3286.c0.m282

I have not tried them on the Norton yet as it still isn't on the road. The Enfield BulletI ownhas one fitted and I was impressed by the way it appeared tocreate a strong vacuum and yes the engine is totally oil tight.Whentherubber pipe and valvewarms up, it becomes very soft and you can actually see the pipe puckering up under the negative pressure it is creating.I was thinking it could be added to the crankcase pipe to assist in the rotary valve action, or any breather pipe that just vents naturally. For example, if someone has added anauxiliary breather pipe to the rocker box it could be added to that. What you have to remember with any breather pipe is that it must not be too long, or if it is, then a large bore pipe should be used. A long, small diameter pipe has far too much restriction and inertia for the exhausting gases to be movedby the rapid pulses of pressure. (see later point)I think its worth a try and experimenting with as it so relatively cheap (especially if one could remove the postage)

If one has chosen to take a long pipe to the rear of the bike. I would still have the valve right up close to the engine, then have a largish volumesecondary buffer chamber to enable the valve to exhaust freely without seeing any restriction and connect the vessel to the long pipe to the rear. (See later)If the buffer chamber is sufficiently large then one can have the advantage that the rear venting pipe can be of a smaller diameter as all it will only have to pass any waste gases in a continuous one-way stream rather thantrying to manage rapidpulses of gas.

As far as I know the timed disc valve Norton breather falls down by the fact that the port holes are tiny and therefore have a big dynamic air restriction. The Duckbill valve does have some slight forward restriction before it opens but seals very effectively against negative pressure. The net result is that a partial vacuum can be created. The greater the vacuum, the less oil flinging around in the crankcase will be blown into the breather, but nearly all breathers will see some oil mist escaping especially if piston ring sealing is allowing large amounts of combustion blow-by. Later Enfields use the breather inside a baffled oil catch-can, situated quite close to the engine and then exhaust the gases to the air filter to be burnt. Periodic drainage is required. The best arrangement will be by experiment.

The rubber pipe can be cut to any length, only the last 2" (the valve) is required for it to function.

Les

This sure sounds like the…

This sure sounds like the breather valve VW used on their 1969 type 3 "Squareback" model, check it out.

Regards,

Albert

Hello You Lot, The Norton…

Hello You Lot, The Norton Manxman 650 ,As a Breather Pipe Of the inlet cover via a banjo under the domed nut .separate parts where made for this machine but it was not fitted to any other machine .my way would be to fit a drill hole 1/2inch by the inside of where the camshaft sprocket lives and tap and thread in there for a breather pipe take off and your pipe would go round the front of the barrels and off to a catch tank via a ball valve , and the air pressure in there would feed oil too your chain via a pipe too the chain-guard as some Chain guards have a pipe welded too the top of the chain-guard near the gusset plate end ?

Hi Folks, There is a massi…

Hi Folks,

There is a massive amount of information on crankcase breathing for Nortons on both the technical pages of this forum and the American Accessnorton website. Many people are posting requests for information when that info is on this very website. (I'm not having a go at anybody here by the way) The general drift on crankcase breathing revolves around creating a small depression in the crankcase and several PCV (pressure control valves) have been used from popular cars. motormite and volvo are some valves used a few years ago. Colorado Norton Works (CNW) make a rather super Carlos Fandango one, (remember him?) but it is very expensive. The Yamaha XS650 twin has one fitted and a German XS650 specialist sells them on his website for about 20Euros. They are neat and come with a small bracket that lends itself to being attached to Commando battery trays or something similar. I have one fitted to my 750 Commando and it works well. Try xs650shop.de I'll have a quick look now and come back with what I find.

Dave

I'm back, www.xs650shop.d…

I'm back,

www.xs650shop.de gets the website, click the union jack for english, engine parts, part No 15_0677 13Euros plus p&p and tax come to about 20Euros I think it's a worthwhile mod, it's unobtrusive and hasn't got Yamaha written on it if you're purist. I fitted mine recently, in a pipe out of the back of the timing cover from the service notes breather mod I carried out about 25 years ago.

Dave

Hi Les sorry not to reply…

Hi Les sorry not to reply sooner but Ive been away got the pipe from Hitchcocks and fitted it on my crankcase breather went for 30 mile run and it worked fine but as time goes by will let you know how it developes. on another note havent got round to fitting a zenor diode yet but will keep you informed.PS i owe yoy a pint for all your help thanks Eddie

I followed exactly what Pe…

I followed exactly what Peter Leslie Howard suggested regarding the breather for my ES2- incidentally best phoning Hitchcock's motorcycles to buy them - and it has worked beautifully with the engine oil tightness much improved. It took me about 15 minutes to install. Cost is about £3 each by the time you take VAT plus p&p into account. Bought one for my Inter butI guess oil tightness there is just a holy grail.

Just one disadvantage so far: I've had to buy a can of spray-on chain lubricant because there's so little coming out of the crankcase breather now.

Anyone else got some really worthwhile and easily executed tips?

Peter Bolton

Dave. Does it matter how f…

Dave. Does it matter how far from the engine the breather valve is fitted? I have 650SS-engined Wideline-framed Dommie which has a large bore breather pipe from the back of the timing chest, which goes to a catch tank in between the oil tank and battery box. Another pipe then goes from there to the rear mudguard stay. Nothing seems to come out of that one, although I have to empty the tank from time to time. The easiest place for me to fit the valve is by the catch tank.Ian

Previously david_evans wro…

Previously david_evans wrote:

I'm back,
www.xs650shop.de gets the website, click the union jack for english, engine parts, part No 15_0677 13Euros plus p&p and tax come to about 20Euros I think it's a worthwhile mod, it's unobtrusive and hasn't got Yamaha written on it if you're purist. I fitted mine recently, in a pipe out of the back of the timing cover from the service notes breather mod I carried out about 25 years ago.
Dave

this valve seems to have been superseded, by one that looks as if it is bolted to engine at a cost of â?60!

The US site will not send to Europe, any other sources?

Charles

I have just found out that…

I have just found out that the XS650 PCV valves are out of stock everywhere, hoping for new stock in October/November.

Previously leslie,peter_ho…

Previously leslie,peter_howard wrote:

As there are frequent messages on this site regarding breatherproblems and modifications I would like to suggestanother one.
There are numerous variations, but the sole purpose of any breather is to vent excess internal gas pressure in an engineand if at all possible leave a partial vacuum.
Nortons have mainly used a mechanically driven disc valve with varying success. However Royal Enfield simply chose to use a rubber one way valve. Yes, Royal Enfields are not famous for their oil tightness but this was due mainly to their construction of independant barrels and poor head sealing. However the rubber "DUCK BILL" valve isVERY effective at maintaining a partial vacuum by simply blowing off excess pressure and sealing immediately when the pressure declined and not allowing air back into the engine. They look just like a rubber pipe so are completely unobtrusive and will go unnoticed on any bike.
These are still readily available from Hitchcocks Motorcyles and are quite inexpensive at £1.65. They can be added to the end ofany breather pipe to add an extra one way valve property. When the rubber pipe of the valve is slightly warm and softened,the effective action can be seen to work, especially at tickover speeds, as the pipe/valve puckers up showing the valve is indeed creating a strong vacuum. If a strong crankcase vaccuum is created, there should be a reduction in the amount of oil blowing out of the breather and a reduction of engine oil leaks.
Hope someone getsa benefit with this.
Les H

Hello Well the Ball valve I bourght from our friendly tractor shop cost all of £6 and alloy ball valve that only goes one way out, and will not let air back in, thses are fitted to most CASE tractors engines as a breather valve, and it works a treat on my bike

All jolly sound stuff. How…

All jolly sound stuff. However, with the Norton timed camshaft breather, theoretically we shouldn't need a separate one-way valve. The breather ports are open on the down stroke and closed on the upstroke, so there not should be a build-up of crankcase pressure - unless of course the bores/rings are out of spec. I expect I have missed something... Gordon.

Ladies & Gentlemen Mem…

Ladies & Gentlemen Members.

I installed a Hitchcock's "duck's bill" breather on my ES2 about a year ago as per Leslie Peter Howard's recommendation. From day 1 it was an outstanding success so I then fitted three to my Inter with an amazing reduction in oil mist surrounding the engine - that was about 9 months ago.

My 1965 650ss is one whereby the crankcase breather exits to the tower on the oil tank so there's nowhere available to fit a duck's bill.

One downside of this mod is that you periodically have to oil the chain because there is so little exiting the crankcase!

One of the best suggestions I have ever seen on this site - thanks Leslie Peter Howard!