It depends greatly upon the filter you are running that hangs down under the air filter. Some people just use the cheap air filter (paper) and once it's saturated it'll drip. Yours looks like it's a better quality and was a good idea to add some extra material to it. Misting will happen no matter what, because alot of it is condensation burning off the oil as the bike heats up (depending on what part of the country you are in). The ultimate trick is to catch it in a can, or make sure your filter can handle the little bit that gets sucked into it. If you follow my posts in the DIY section, you'll see my original catch can. I welded it out of aluminum, had a breather filter on top and ran braided line from the air filter. Unfortunately the breather filter would pull in extra mist from the vacuum and I got tired of draining the can after every ride. That was my way of being EPA friendly. Wicking is when a piece of material is actually drawing out fluids through direct contact and absorbancy. Vacuum is when air rushes over an open surface created a "draw or pull". Given where your small can is, it's likely a vacuum. The milky/oily is water/oil/air mix (mist/vapors) as it draws through the line. Thanks btw, the stainless tubing is just a simple way to run it and make it look semi nice lol

 

Once a filter gets any oil in it at all, the venting will almost stop. There's hardly any pressure coming out of crankcase; it's pretty much just passive venting. Automotive engines have PCV (positive crankcase ventilation) and use intake vacuum to pull the vapors out. Personally, I'd never put a filter on my breather because of that. I just vent it out through the bottom.

 

Thanks for the tip. I think I have some K&N pre-filter foam left that should do the trick for that. I can ride for miles and have no problems, but a couple of high RPM runs and the outside of the catch can will get wet, maybe even a drip or 2.

 

Can you clarify the reason once the filter gets oil the venting stops? I have a filter at the end of the hose and there is consistent gunk dripping out of the filter frequently.
I want the breather to be effective so this is interesting feedback

Cheers!

 

Sure. I forgot what you asked after seeing your Avitar LOL!!!
Your filter will drip once it's saturated with oil. Gases (air) have a much harder time passing through a clogged media such as an oily filter. The only thing a filter on your breather hose does is it stops oil mist from dripping out of the tube; you don't need to worry about filtering the air in because it's only flowing out. With your engine running, block the end of the hose with your finger. It will stop the flow easily because it's only passive flow; not active flow. There's no force pushing it out other than blow by which shouldn't be very much. You want those gases out of the crankcase because they're dirty and will build up inside your engine. Any restriction of the outflow will reduce venting by a lot due to the small amount of pressure pushing outward. If anything, it would be best to have an active flow and that would mean hooking it up to a vacuum pump or as in automobiles, intake vacuum. Actually, the stock set-up does use a type of active flow because the vent hose is connected to the outside of the intake which will pull the vapors in. Not a lot, but it will pull. I remember one time I removed my dipstick to check the oil after a long run. There was a burst of suction when I removed the cap. That had to be from the negative pressure from the stock venting tube.

 

The filter media I am using is just to keep any moisture from following the air, vapors, whatever out. I could see if the filter media was to become soaked in fluids, then it could/would maybe, restrict venting or the breathing of the system (because it would have to have enough flow to push thru the liquid, and being relatively a passive flow it may not have that kind of pressure)... luckily, my filter material does not get saturated at all, it is more a preventative thing than anything. Initially when I did this bypass, the filter media was touching the top of the catch-can, where the vent holes were. Any moisture that was passing thru the filter would track with the air to the top of the catch-can and weep/wick, whatever, around the top, but not even a drop, I would just see it there if I was paying attention. I decided to use a more porous material and make it thinner so there's gaps on both the top and bottom and that alleviated that. There's plenty of ways to skin this cat, but it does pay to pay attention... I could see where if you have quite a bit of blow by, or run you oil topped of to the full full line all the time it could become an issue possibly. I just offered up what worked for me... I may not have been experiencing the same challenges others have had to figure out.
DAmn GhostRider, I wish I could juggle lol

 

Thanks for the feedback! I am sorry Lisa Ann got you al distracted She is something else!

 

I've followed the discussions on multiple forums regarding venting directly to the atmosphere versus a filter on the end for many years. I have always run a filter in the past but, with my new S&S install, I decided to vent straight to the atmosphere. Yesterday, I had the brilliant idea that maybe asking S&S what they thought about the debate might be a good idea (since the motor is under warranty). Turns out they recommend a filter since "there is some air moving in both directions". I asked about the umbrella valves being one way and they said that is a common misconception. According to S&S, the umbrella valves main purpose is to separate oil from air, not to act as a check valve. Since they are the motor builder experts, the filter goes back on. Just a heads up.

 

Quite a bit of air movement depends greatly upon where the filter is located, or straight tubing. If it's out of the wind then there shouldn't be any real problems. Or if you have a long enough run/narrow tubing then the crank compression will overpower the air flow pushing back in. Problem I had with my catch can before was because the filter was into the wind. So ya, the can would do it's job, catch any misting/moisture. But if it filled up a little bit, then at highway speeds the it would create just enough vacuum to draw some mist out. Didn't happen often, but it was because I made sure the can was always empty. It was located at the front of the frame on the left side. Most catch cans are further back and buried behind the engine, etc. Just wanted an easier option for draining is all (petcock on the bottom). The 1/4" tubing has a pretty small ID so there's no worry of any back pressure being forced into the engine, nor will it create enough vacuum to draw it out. The guys that run the open filter underneath the air filters may get a bit more, but again, that depends greatly on the filter and surface tension of oil once it saturates the filter plus air exposure/speeds, etc. And like the oil problem to begin with, it's different for everybody. Sometimes that's half the fun, experimenting, designing and building. Spent so many years doing prototype powertrain development and now that I'm not involved in that industry anymore, it's nice to be able to wrench/weld and engineer again.