Anyone done this?

Hey Guys,

Never thought I'd start a breather thread, but just a quick question. Has anyone ever done this this mod for a 71, using the 72- breather mounted to the timing case blanking plate? The only place I've seen done is by Oldbritts http://www.oldbritts.com/11_061542.html
Just wondering why I've not seen it here before, is there a problem with the 72 breather?

Basically, I like the fact that I don't need to have a hose going to valve, keeping the setup as clean as possible. I run Mikuni without the stock airbox so there's not a lot of places to hide things. Currently I've got cheap plastic Motormite breather, it works, but doesn't last long.

Yes, I made my own flat backing plate and put a reed typle valveassembly on. seems to work fine

Thanks Moto,

How long have you been running this? Does the breather require any maintenance?

Cowboy Don said:

Hey Guys,

Never thought I'd start a breather thread, but just a quick question. Has anyone ever done this this mod for a 71, using the 72- breather mounted to the timing case blanking plate? The only place I've seen done is by Oldbritts http://www.oldbritts.com/11_061542.html
Just wondering why I've not seen it here before, is there a problem with the 72 breather?

Basically, I like the fact that I don't need to have a hose going to valve, keeping the setup as clean as possible. I run Mikuni without the stock airbox so there's not a lot of places to hide things. Currently I've got cheap plastic Motormite breather, it works, but doesn't last long.

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Are you asking about using the Combat breather on the blank timing plate? Or just running a large breather off that blanking plate in general?

In the past I followed the INOA tech guide and various tech discussions in Norton club newsletters saying the bigger the better for a breather. In other words,, the larger the ID of the tube the better. When running its amazing the volume of air being huffed thru there, In my opnion thats the most important part,, providing large capacity for breathing.

In customized Nortons,, ive made several variations, One with a version of the Motormite but a metal canister,, I think it was an old Chevy PCV valve,, they last longer when you keep them a bit away from the motor,,eventually they all give out becaus that air flow is very violent. In some cases we just used an open breather K&N style breather, others we T'ed into the oil tank and a pipe out the back by the lic plate (ala late 60s and early 70s Triumph) and a few into the air cleaners.

The Combat style of breather assy is kind of a good choice as it has a metal mesh screen inside and keeps the rocks trees and boulders out, and acts a little as a baffle for the inevitable oil that wants to migrate up the pipe, plus its relatively large bore I.D. the issue is how are you going to route the accompanying pipe? Racers require a oil catch can, or you can fling it onto your drive chain or out the back of your bike and soil mother earth. Besides the air volume you will always get some degree of oil sputtering out the breather.
theres a LOT of opinions on this and almost as hotly debated as whats the best motor oil.

most would agree the early style breather off the end of the camshaft is WAY too small and inadequate, however at one time I did have a shop customer who agreed to have me modify his breather (Ype, BIG brass Pipe fitting onto his blanking plate) he strongly agreed about the volume of air coming out of it, but oddly, when I saw the bike again 6 months later He had removed it, went back to the stock breather off the cam, and said he read about this topic online and decided somebody on some internet forum knew more about this topic and went with his advice. So. oh well, its his bike, his problem

I'm in the process of upgrading the breathing as part of the full rebuild of my 70 model. I drilled the cases for timing case breathing, and I thought about using the Combat fitting, but it wouldn't suit my setup.
I've made a canister to fit between the engine and gearbox, with a MikesXS reed valve attached to it. The reed valve's intake tube points directly at the timing case blanking plate, so the right-angled Combat fitting was unsuitable.
You're right, there isn't much space available, so everything needs to be neat and compact. The canister will vent into the airbox. It's got to be better than pumping crankcase fumes into the oil tank.
The breather hoses are 1/2" bore and the hose run will be very short.
Cheers
Martin

Cowboy Don said:

Hey Guys,

Never thought I'd start a breather thread, but just a quick question. Has anyone ever done this this mod for a 71, using the 72- breather mounted to the timing case blanking plate? The only place I've seen done is by Oldbritts http://www.oldbritts.com/11_061542.html
Just wondering why I've not seen it here before, is there a problem with the 72 breather?

Basically, I like the fact that I don't need to have a hose going to valve, keeping the setup as clean as possible. I run Mikuni without the stock airbox so there's not a lot of places to hide things. Currently I've got cheap plastic Motormite breather, it works, but doesn't last long.

Click to expand...

I wouldn't do that, if I had a non-72 I'd get the CNW/comnoz Sump Breather and blank off the timed breather. Breathing through the timing case is stupid. Just tiny little holes from the crankcase to the timing case. Like trying to breathe through a coffee stirrer.

swooshdave said:

I wouldn't do that, if I had a non-72 I'd get the CNW/comnoz Sump Breather and blank off the timed breather. Breathing through the timing case is stupid. Just tiny little holes from the crankcase to the timing case. Like trying to breathe through a coffee stirrer.

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+1 In addition to that what can't get through the holes just gets compressed and expanded inside the crankcase. The valve in the timing chest doesn't see the theoretical peaks and valleys caused by the swept volume of the pistons. It's the difference between them that is the driving force behind the 'vacuum pump'.

Cowboy Don said:

Hey Guys,
Basically, I like the fact that I don't need to have a hose going to valve, keeping the setup as clean as possible. I run Mikuni without the stock airbox so there's not a lot of places to hide things. Currently I've got cheap plastic Motormite breather, it works, but doesn't last long.

Click to expand...

Jim's sump valve is about as clean as it gets. You can't see it.

Just make sure if you have a pre-71 frame that you have clearance for the valve because of the brace. It wouldn't fit on mine.

Dave
69S

On Ms Peel Combat I moved oil pick up to rear, blanked off the low breather port and attached the factor cool looking baffle on back of the magneto flat with a Krank PCV inline near the spinal tube. I garantee I ran the living snot out of Peel nearly 8000 at times and spend every possible sane open at over the ton. Even after the over rev event that knocked her power down i could run a kinex or Q-tip in bottom end of breather hose and got no None NADA even oil mist evidence and the clear plastic tube stayed clear but for age yellowing. Only the SS nuts and new cadmiun hardware didn't get rust patina w/o factory oil protection.

swooshdave said:

Cowboy Don said:

Hey Guys,

I wouldn't do that, if I had a non-72 I'd get the CNW/comnoz Sump Breather and blank off the timed breather. Breathing through the timing case is stupid. Just tiny little holes from the crankcase to the timing case. Like trying to breathe through a coffee stirrer.

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If you have the chance when the motor is apart, there are places to add holes thru the case near the timing pinion, Its well documented on how to do this, for one source the INOA tech guide (vol 2 & 3 at least) showed the procedure. works quite well. also a lot easier on your wallet, works well. OR,, buy the shiny bling. Your choice

Right don't have to remove the DS baffle lip and can put screen like holes
in the TS sump return passage, which can keep out blow up pieces from
also damaging oil pump or jamming inside expanded heated oil ways to be trapped once cold.

Thanks Guys,

Not planning on having the engine apart anytime soon (knock on wood), so I'm looking for something external. I like the idea of Comnoz's sump breather, but it's a bit rich at the moment. Maybe I'll throw a new Motormite on there for now and save some cash. Gottta shell out for a new rear tyre next week!

as has been pointed out here by jim comstock after PROPER testing and not he said she said along with common reasoning the crankcase NOT the timing chest is THE place to vent it along with a reed valve. you cannot make the passages large enough to pass 750CC's + of air into the chest to make a truly effective breather.
Will the timing chest setup work? yes it does BUT it is an old way of thinking.

internetannoyance said:

If you have the chance when the motor is apart, there are places to add holes thru the case near the timing pinion, Its well documented on how to do this, for one source the INOA tech guide (vol 2 & 3 at least) showed the procedure. works quite well. also a lot easier on your wallet, works well. OR,, buy the shiny bling. Your choice

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Hey CowboyDon.
FWIW, Adding a breather to the timing side as it sits can do no harm. I have a 72 and have the timing side machinedto except a breather and the holes opened up to allow better air flow to the chamber.

I continue, I also have the breather coming out the bottom left rear (stock) with a Mike's XS unit mounted at the 90 degree area high. I had it blocked of for some time and all was well with the timing side breather, but I said to myself "Hey Pete, if one is good, how about two?" Anyhow, they both breathe effectively.

I guess the point is, you can improve what you have with little effort, maintaining your current breather and simply adding another off the timing mag boss cover. I have an extra 72 breather if you want it.

No need to complicate this issue. This is just common sense and a simple improvement.

Hi Pete,

My mag cover is where I'm breathing withe Motormite at the moment. I just wanted to improve on the current setup and the 72 breather looked like an affordable and clean way of doing that. PM me about your spare breather.

Thanks Mate!

In a past detailed thread on the actual pressure measures Jim reed valve gave I politely challenged him and list about the significance of how efficient the evacuations system is - to get admission, anything beyond just keeping pressure low enough oil stays sealed is over kill, but the lower the pressure maintained, there's a few extra hp to be gained, -if you rev high enough to obtain the over kill benefits. So unless you like to take on sports bikes or vintage in competition it may not matter so ya can tell. The reed valves would allow more ring wear blow by before weeps appear so its better than regular PCV's in that regard too. The easiest breather to install is the 90's Motormite that just replaces the 90's fitting that turns breather hose from vertical to aim horizontal into tank. It may not be as efficient at a closer mount but it rather cooler gases by that point so the cheap ass valve lasts longer while still keeping leaks at bay. Still when push come to shove none of the above passive breathes can keep up with an active evacuation system.