For those with pods - what to do with breather hose?

[Steve]

A PCV valve requires a relatively constant vacuum source to operate properly. Cars have no problem, as they have one set of throttle plates that feed a common plenum (intake manifold) that will have plenty of vacuum. On the other hand, our bikes only have a rather short intake tube between the throttle plate (or slide) and the engine, so the vacuum pulses. And if you vent the crankcase into that one runner, it will upset the air/fuel mix on that one cylinder.

There are a few methods of catching the mist. There are wire mesh screens in the valve cover and breather cover that will catch most of the oil. If you are not terribly concerned with environmental concerns, you can just route a longer hose from the breather cover along the frame, down to a point below the swingarm pivot. Cut the end at an angle, there will be a slight vacuum formed, it will draw any vapor away from the engine.

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[ben2go]

Thanks for the explanation and the quick response, ben2go.

Would there be any benefit to a PCV valve, or would a simple catch can suffice when going from airbox to pods? If you do use a one way valve, do you have to hook it into the intake somehow or are folks just doing that so they don't get an oil mist on the bike?

You're welcome and Steve go it. I use a simple K&N filter on the breather hose. I don't get any oil out of it but it does get black from grim. I clean it once a year when I clean my air filter.

[KEITH KRAUSE]

I run a longer crankcase breather hose to a K&N breather filter under the seat. For a catch, I used the plastic upper dust cap from some Progressive shocks. I used a piece of 2" electrical tape to seal the hole in the cap. Mounted the cap upside down with a groove cut into it for the hose and filter to sit in. Mounted the cap to the frame crossbar under the seat with a tie strap. I cut out a little "drip pad" from a paper towel and placed it in the cap. I've replaced the pad a few times in 20 years but it doesn't really need changing. I never get any mist to speak of. Only time I've seen any discharge was after HARD riding AND putting in a little too much oil at the last oil change.
You could make an even better looking catch with a 3" PVC cap.
I used to have a pic of mine on this site but I don't know where it is now. Too stupid to provide a pic now.

[solarae]

I haven't got anything at all hooked to the metal breather on the valve cover. It's totally clean and as long as it stays that way I don't see a need to do anything.

[Sam 78 GS750]

Thanks guys. So a PCV valve would need a vacuum to operate then, and the pressure coming out of the engine wouldn't be enough to open the valve.

Earlier in this thread some folks split the hose off the breather cover and routed to each carb to avoid the unbalanced airflow issue Steve mentioned. Some used the carb sync ports, and others drilled holes in the pod covers and attached hose fittings. If I were to go this route, I think the carb sync ports would be the cleanest option...

Is there any benefit to using a PCV valve on a GS though?

I've done a bit of googling on crank venting, and I think I have a basic understanding of the issue at hand. What I read in this thread seems to confirm what I read in other places online, where folks I respect on the forum said that some crank leaks were stopped after addressing the issue.

The original design had the breather hose routed to the airbox, which would imply some vacuum from the intake. By now routing it to just a K&N filter or a catch can, would I be introducing crank pressure that was being relieved by the original design?

[TxGSrider]

Some ATVs use a type of PCV valve and this place used to sell a really nice one but I don't see it on their site any more http://thumperracing.net/index.php?route=common/home . Ive been using one on my KTM powered quad. It uses a piece of rubber inside to act as a valve and its rebuildable and when I shut the quad off it makes a groaning sound from the vaccum release. I don't know how it would wok on our bikes. On my GS I just have a hose and a K&N filter on the end and I never notice any oil dripping out of it or anything.

[ben2go]

Thanks guys. So a PCV valve would need a vacuum to operate then, and the pressure coming out of the engine wouldn't be enough to open the valve.

Yes, and they could plug up over time and cause seal leaks or blowouts. I believe that's why motos do not have them. An oil leak on a motorcycle can cause a bad wreck. Think blown oil seal coating rear tire in said oil. If I understand moto carbs right, vacuum reduces a lot as the throttle plates up to allow more air flow.

Earlier in this thread some folks split the hose off the breather cover and routed to each carb to avoid the unbalanced airflow issue Steve mentioned. Some used the carb sync ports, and others drilled holes in the pod covers and attached hose fittings. If I were to go this route, I think the carb sync ports would be the cleanest option...

It would be the cleanest option in my opinion. The oil mist, if any, would be burnt off instead of going into the air, on the road, on the rear tire, or on the bike somewhere.

Is there any benefit to using a PCV valve on a GS though?

Check my earlier response for my opinion on it.

I've done a bit of googling on crank venting, and I think I have a basic understanding of the issue at hand. What I read in this thread seems to confirm what I read in other places online, where folks I respect on the forum said that some crank leaks were stopped after addressing the issue.

This is true on motos and cars. Removing the PVC, or in our case the breather to airbox connection can improve scavenging the crankcase pressure if direct vacuum is applied to the breather hose and thus the cranckcase.

The original design had the breather hose routed to the airbox, which would imply some vacuum from the intake. By now routing it to just a K&N filter or a catch can, would I be introducing crank pressure that was being relieved by the original design?

Well, it can be debated that the placement of the breather hose could see a positive pressure because of the rush of incoming air into the airbox as the engine sucks it in could potentially cram air into the breather tube port as the air rushes in. Even if the breather tube sees vacuum, it's no where near that of a direct vacuum connection from the engine.

These are just my opinions. I have used different designs depending on the engine and how it breathes. If I notice a lot of oil through the breather tube, I use a catch tank with a filter to vent off any pressure. If I'm looking for all out performance and want to pull pressure out of the crankcase, I use the direct connect to the intake method. On a few applications, I have done both the pod connection and the filtered breather tube solution. Not at the same time obviously. To be honest, it really depends on how your bike breathes and whether or not it mists enough oil to need to be tanked or little enough to burn or just filter into the atmosphere. Older more worn engines tend to lose more oil mist through the crankcase vent than a fresh tight engine.

[KEITH KRAUSE]

As I said 5 posts back, I have a K&N filter at the end of the hose and it sits in a catch. I've never had any problem related to crank breathing. That's how it will stay.
I haven't read anything in detail about crank breathing or venting or whatever you want to call it, so maybe my opinion is useless.
The part we're talking about here is called a crankcase VENT hose. It's to vent the crankcase. I believe the factory connects it to the airbox as a matter of convenience. No leakage, fumes and no additional part needed to properly terminate the end of the hose. Like the vent on a gas cap vents the gas tank, it's purpose is to vent the crankcase. I don't see the need for vacuum in such a simple system. It vents like it is. It vents with a filter on the end.

[scratch]

As I said 5 posts back, I have a K&N filter at the end of the hose and it sits in a catch. I've never had any problem related to crank breathing. That's how it will stay.
I haven't read anything in detail about crank breathing or venting or whatever you want to call it, so maybe my opinion is useless.
The part we're talking about here is called a crankcase VENT hose. It's to vent the crankcase. I believe the factory connects it to the airbox as a matter of convenience. No leakage, fumes and no additional part needed to properly terminate the end of the hose. Like the vent on a gas cap vents the gas tank, it's purpose is to vent the crankcase. I don't see the need for vacuum in such a simple system. It vents like it is. It vents with a filter on the end.

Where is the "like" button?
Old brittish bikes just vent via straight tube to the pavement. The filth that the a motor vents is chock full of hydrocarbon rich gas that mix with vaporized oil and water yer motor makes, that dirty escaping gas creates smog. Sine 1964 the epa said one must collect that vapor to slow down the smog.

All you need is a filter to collect the oil vapor that's in the vented gasses. I ran an old sock zip-tied to the end of the tube once, sock wasn't usable after that but... the bike really didn't care and it caught the smog-making oily steam.

[red1100]

I’ve got the K+N on my breather hose and I really don’t like it. Been thinking about trying to run individual lines to the engine side of the K+N pods at the bottom,possibly a small,maybe 1/4” tube,possibly brake line tubing to make a PCV system. Anyone tried that?

[Sam 78 GS750]

I’ve got the K+N on my breather hose and I really don’t like it. Been thinking about trying to run individual lines to the engine side of the K+N pods at the bottom,possibly a small,maybe 1/4” tube,possibly brake line tubing to make a PCV system. Anyone tried that?

Read back through the rest of this thread. A few folks have done that, and they posted pics and details...