Breather Box / Oil Air Seperator

Gojuu · Feb 10, 2022

I'm hoping someone can help me understand this.

My bike has a breather box "fix" installed and I've read a lot of issues around people having issues with oil in airboxes and with breathing of the bikes. I don't seem to have any.

The understanding I have of the breather box is that prior to them being fitted as a fix the crank case vented to the right side of the rocker cover, vented through the rocker cover, and then to the air box.

Assuming I have that right, what I don't get is, what happens in the "magic black box" that didn't happen when vented to the rocker cover, if that makes sense?

Gojuu · Feb 11, 2022

Aaaaand, while I'm asking, this isn't factory, is it?

(yes, I will clean the water stains before I refit it.........)

BritTwit · Feb 11, 2022

Never heard of a breather box on a 961.
Where is this breather box fixed to you bike?
Can you provide a photo of the box in situ?

cliffa · Feb 11, 2022

BritTwit said:
Never heard of a breather box on a 961.
Where is this breather box fixed to you bike?
Can you provide a photo of the box in situ?

I think Gojuu is referring to the breather separator update.

lcrken · Feb 11, 2022

Are you talking about the air/oil separator, a small in-line black box fitted to the breather hose from the crankcase. There was a breather update kit for the earlier models that included it, plus some hose re-routing, filters, check valve, etc.

Ken

TonyA · Feb 11, 2022

Gojuu said:
Aaaaand, while I'm asking, this isn't factory, is it?

View attachment 84901

(yes, I will clean the water stains before I refit it.........)

Yes , That is factory fitted breather plate and RTV. And the black box oil/air separator is just that . There is a low restriction baffle that the vapors run through , hopefully collect and run back to the crankcase. Most of the oil in airbox problems are related to blow by past the rings/pistons. When fitted with properly sized piston/barrel and rings , there is virtually no oil in air box issue. You may be one of the good ones out there ! I think iwilson runs a variation of this that uses the crankcase to rocker cover and then he sends it out to small air/oil separator and then to air (I think). This is working well for him he said. Also, I am running kind of a similar setup , that I would call a primary and secondary system and will post when it gets warmer here . But either way , I will incorporate the air/oil separator in any variation , whether before the rocker box or between crankcase air box or crankcase to air. Or conversely , you can search my posts and find it somewhere on this forum. Keep up the great work , you are really going to enjoy this bike !

TonyA · Feb 11, 2022

Look up thread ( Inlet Upgrade ) lot of info there . Here is the thread :

Inlet upgrade?

Years ago an upgrade I carried out on a Rocket 3 was from 28 to 30mm carbs and the improvement was great, might of helped that I tapered the adaptors for them but I digress. Now the 961 has 38mm throttle bodies, are 40mm worth thinking about? Surely there's an formula for this but just thinking...

www.accessnorton.com

Gojuu · Feb 11, 2022

Gents - you’ve all understood me - yes, the black plastic oil air separator. Sorry for the terminology.

What I am trying to understand is, if the air/oil goes from the crankcase to the separator - I’m guessing the ideal situation is that the vapour is separated and the oil travels back to the crankcase, whilst the air vents to the airbox - then why couldn’t / didn’t / won’t this process happen using the rocker cover as the seperatorr?

My bike currently has the left and right rocker banjos simply looped together.

What I’m trying to do is, tidy the bike up a bit, and make it simpler where it can be. If that loop rocker doesn’t do anything, I was just going to blank it, but when I got the rocker off, saw that plate in the rocker, I started wondering why it couldn’t be used?

cliffa · Feb 11, 2022

Here's what iwilson did...

Unraveling the 961 part two (oil in the air box)

There are two shortcomings with the 961 that have annoyed me the most. One is the idle which I've been investigating HERE The other is oil in places it shouldn't be! Neither unfortunately can be fixed with a cable tie! So this thread is going to deal with understanding the oil in the airbox...

www.accessnorton.com

TonyA · Feb 11, 2022

Gojuu said:
Gents - you’ve all understood me - yes, the black plastic oil air separator. Sorry for the terminology.

What I am trying to understand is, if the air/oil goes from the crankcase to the separator - I’m guessing the ideal situation is that the vapour is separated and the oil travels back to the crankcase, whilst the air vents to the airbox - then why couldn’t / didn’t / won’t this process happen using the rocker cover as the seperatorr?

My bike currently has the left and right rocker banjos simply looped together.

What I’m trying to do is, tidy the bike up a bit, and make it simpler where it can be. If that loop rocker doesn’t do anything, I was just going to blank it, but when I got the rocker off, saw that plate in the rocker, I started wondering why it couldn’t be used?

It may work just fine , try and see.

BritTwit · Feb 12, 2022

Gojuu said:
Gents - you’ve all understood me - yes, the black plastic oil air separator. Sorry for the terminology.

What I am trying to understand is, if the air/oil goes from the crankcase to the separator - I’m guessing the ideal situation is that the vapour is separated and the oil travels back to the crankcase, whilst the air vents to the airbox - then why couldn’t / didn’t / won’t this process happen using the rocker cover as the seperatorr?

My bike currently has the left and right rocker banjos simply looped together.

What I’m trying to do is, tidy the bike up a bit, and make it simpler where it can be. If that loop rocker doesn’t do anything, I was just going to blank it, but when I got the rocker off, saw that plate in the rocker, I started wondering why it couldn’t be used?

Wasn't there someone a while ago who indicated that on hard braking, especially going down hill, oil could flow into the vent line that runs from the rocker cover to the oil tank, and allow oil to flow back from the tank into the rocker cover?

TonyA · Feb 12, 2022

BritTwit said:
Wasn't there someone a while ago who indicated that on hard braking, especially going down hill, oil could flow into the vent line that runs from the rocker cover to the oil tank, and allow oil to flow back from the tank into the rocker cover?

Yes , That is correct and why Norton lowered the oil level in the tank too . And the best way to get crankcase pressure out is directly out , not through the rocker cover. If Gojuu tries it both ways he can decide which is better. l know when I had it the old way (through the rocker cover) , I had oil in my air box especially at freeway speeds 70-75 mph . If he is trying to clean it up , block off the banjos like some others have done which looks good. But please try your experiment first .

Gojuu · Feb 25, 2022

So, I think I've copped out. I read what I could and never came to a conclusion that convinced me I would improve it. It's worth noting my bike hasn't had an oil in airbox issue, so I'm not really trying to do anything but clean it up.

What you probably can't see in the photos is how awkward the rocker "loop" was. It was pretty much jammed against a whole bunch of parts around the injectors and throttle cables, and it really was out of place. Having had that apart a few times now, it annoyed me every time - especially knowing it did nothing.

So tank, rocker etc all off and this:

was replaced with:

I'm pretty happy with the outcome. In the scheme of things it probably isn't major, but I'm happier with it. It gave me the space to route some of the cables better and I routed the now unused IAC connector up under the tank and sealed it off:

TonyA · Feb 26, 2022

It looks much cleaner .

iwilson · Feb 28, 2022

But you still have that ugly oil separator box there! Although beauty is in the eye of the beholder.

Gojuu · Feb 28, 2022

iwilson said:
But you still have that ugly oil separator box there! Although beauty is in the eye of the beholder.

View attachment 85428

@iwilson - trust me I am completely aware it’s still there. I’ll end up coming back to this……..

iwilson · Feb 28, 2022

Gojuu said:
@iwilson - trust me I am completely aware it’s still there. I’ll end up coming back to this……..

I have no doubt! You're clearly a man on a mission. Note the above photo still had the clear breather tubes I fitted to observe what exactly was going on!

TonyA · Mar 5, 2022

Gojuu said:
@iwilson - trust me I am completely aware it’s still there. I’ll end up coming back to this……..

The later type oil/air separator hose were different then the early one you have. On a Domi , they had to run it in your current position . But on later Commandos the box is positioned higher and closer to the airbox , so you see much less of it. And I think it looks better . Have a look at a late model 961 Commando and see what I mean.

Gojuu · Mar 5, 2022

TonyA said:
The later type oil/air separator hose were different then the early one you have. On a Domi , they had to run it in your current position . But on later Commandos the box is positioned higher and closer to the airbox , so you see much less of it. And I think it looks better . Have a look at a late model 961 Commando and see what I mean.

I know exactly what you mean. Are they the same seperator? I think it looks better as it seems much more hidden behind the frame to my eye.

TonyA · Mar 5, 2022

The separator is exactly the same , what is different is the hoses they used to reposition it.

Breather Box / Oil Air Seperator

Gojuu

Gojuu

BritTwit

cliffa

lcrken

TonyA

TonyA

Inlet upgrade?

Gojuu

cliffa

Unraveling the 961 part two (oil in the air box)

TonyA

BritTwit

TonyA

Gojuu

Attachments

TonyA

iwilson

Gojuu

iwilson

TonyA

Gojuu

TonyA

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