Considerations for doing a "breather mod"

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pash
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Considerations for doing a "breather mod"

Postby pash » Thu May 07, 2009 10:03 pm

Work In Progress :lol:

Why does my engine need a breather
A Buell needs one for two main reasons:
i. Because during combustion, some gas is forced past the piston rings (this goes for all engines)
ii. Because there is an uneven firing interval, resulting in the volume inside the crank cases not being constant (this is a Buell peculiarity)

If there was no breather, the pressure in the engine would build up and you would blow a seal to allow gas to escape.

How does it work from the factory?
On Buells, just as on many other engines, the breather is routed from the top of the engine (rocker covers) into the airbox. The gas forced past the piston rings, known as blow-by, exists into the inlet airstream along with any oil picked up along the way.

What is the issue?
The oil, picked up along the way, tends to make a mess in the airbox. This mess can mean clogging of the air filter element and contamination of the temperature sensor. A pureist might also say that the blow-by contains Carbon Dioxide, which is no use for combustion and hence power or drivability.

What are my options for modding?
There are plenty of ways to do this, but they fall into three main categories.

i. You can vent the breather to atmosphere
ii. You can run the breather to a catch can with a vent to atmosphere
iii. You can run the breather to a catch can with a vent to the airbox

Regardless of which solution you choose, you need to ensure that in the removal of brether pipes from the airbox, you block any holes up. This is important as the breathers vent downstream of the filter and hence any leaks would mean unfiltered air is allowed to enter the motor.

i. Venting the breather to atmosphere
Regardless of what anyone would have you believe, Buells do not spit much oil out of the breather pipes. If they did, you would be topping your oil up continuously and replacing air filters at very regular intervals. For this reason, it is quite acceptable to vent to atmosphere with no catch tank.

When you route the pipe, you need to make sure that any oil mist exhausting from the pipe does not find it's way on to the tyres, brakes, belt etc.

The addition of a filter at the pipe exit just means that it will get clogged with oil over time and will stop acting as a breather, resulting in blown seals.

ii. Running the breather to a catch can with a vent to atmosphere
A catch can is used to seperate the oil from the gas, the gas being allowed to flow to atmosphere afterwards.

Again, the addition of a filter at the pipe exit just means that it will get clogged with oil over time and will stop acting as a breather, resulting in blown seals.

iii. Running the breather to a catch can with a vent to the airbox
As above, but with the gas exhausting to the airbox.

The design of a good system
The design of a good system relies on the understanding of what you want to do and an understanding of simple physics.

What do you want to do?
The straight forward answers are:
i. Stop oil getting into my airbox (smoother running / cleaner filter / no oil on my temp sensor)
ii. Stop oil getting onto my tyres/brakes/belt

The simple physics?
Gas is lighter than oil



******


Emotive subject. I started putting something together to provoke thought and an understanding as to why you are doing what you are doing. If you are happy to follow someone elses implementation without understanding, then that is fine, but i doesnt work for me.

Questions you need to ask yourself are:
1. What is wrong with the stock set up?
2. Am I going to let the engine dump it's spew overboard
3. Am I going to let the engine dump it's spew into a catch can
4. Am I going to let the catch can breathe without a filter
5. Am I going to let the catch can breathe with a filter
6. Am I going to let the catch can breathe into the airbox

1. My XB12R has the stock breather setup and you will be hard pressed to find a smoother XB
2. My S1 spews it's guts overboard - it has XB rocker covers and PCVs and has a Forcewinder - it drips on the garage floor from time to time
3. I would only use a catch can if I was forced to - I don't want to have to empty it
4. If I had a catch can, I would let it breathe to air
5. Filters can clog. If they clog, you end up with an increase in crankcase pressure and this can be the straw that breaks the camel's back for tired seals and filters (I had an S1 that blew the oil pump gasket)
6. An easy solution, but not much different to the standard set up as there will still be oil mist in the gas and the gas will be high in UHC and/or CO2 as it is combustion that that forces gas past the rings and into the crackcase

So, bear these things in mind...
08 Specialized Langster

GX07
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Re: Considerations for doing a "breather mod"

Postby GX07 » Thu Jul 23, 2020 10:14 am

Thank you for this informative post Pash.
My Uly has stood for a while and once cooled down after a good run there was a cream coloured puddle under the engine breather pipe which prompted me to have a look for articles on the topic.

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deepsix
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Re: Considerations for doing a "breather mod"

Postby deepsix » Thu Jul 23, 2020 7:49 pm

A good technical post about Buells. A breath of fresh air :old:
I'm a Hornithologist, I get excited by exotic birds.........

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mojomick
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Re: Considerations for doing a "breather mod"

Postby mojomick » Thu Jul 23, 2020 9:13 pm

I run mine into a Red Bull can. Mainly because the colour almost matches.....
I started out with nothing and still got most of it left.

Jones
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Re: Considerations for doing a "breather mod"

Postby Jones » Fri Jul 24, 2020 2:12 am

Mine vents to atmosphere, only a few drops of moisture when cold then next to nothing when warm.

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barney
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Re: Considerations for doing a "breather mod"

Postby barney » Fri Jul 24, 2020 8:41 am

Jones wrote:Mine vents to atmosphere, only a few drops of moisture when cold then next to nothing when warm.

:yt: :yup:
GX07 wrote:Thank you for this informative post Pash.
My Uly has stood for a while and once cooled down after a good run there was a cream coloured puddle under the engine breather pipe which prompted me to have a look for articles on the topic.

that cream coloured puddle after a good run , says to me lots of moisture in that oil :shock: , you need to get it warmed up (hot) then change the oil :idea:
Buell Ulysses XB12X 06/08

gusm2
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Re: Considerations for doing a "breather mod"

Postby gusm2 » Sat Jul 25, 2020 1:03 am

mojomick wrote:I run mine into a Red Bull can. Mainly because the colour almost matches.....


I used to have mine into a neuky broon can, mainly because I drink lots of it :)
Last year I joined a group for anti-social people
We haven't met yet.

gusm2
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Re: Considerations for doing a "breather mod"

Postby gusm2 » Wed Jul 29, 2020 12:13 pm

Last year I joined a group for anti-social people
We haven't met yet.

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conquistador
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Re: Considerations for doing a "breather mod"

Postby conquistador » Wed Jul 29, 2020 8:29 pm

You'd be hard put to spot the difference between the original and more recent contents...
2001 X1
2001 M2
2017 Street Triple RS
Wilier La Triestina
Scott CR1


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