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Here is my opinion since this is just a discussion. It is based on my 46 years as and engineer and working on bikes as a hobby longer.
If you fill you are above the law, (and that is fine with me) put a filter on the end of the hose. However, I like you doubt the fluttering could be enough to let much air come back. If you were to remove the valves like another poster, I sure would. No big deal.
However I disagree with you from my experience with a stock Harley and the stock positions of the vent hoses letting raw oil into the intake. The air flow just is not fast enough. The engine does not suck air in like it blows it out the exhaust. As the pistons drop down, they create a vacuum and the apx 15 lbs atmospheric pressure rushes in. Sure, it sucks vent gasses but not oil. That actually runs down out of the hose when bike sets. That is why with an open filter, you see a bunch after bike is not used for a long time. You can see how clean your butterfly is in your picture. Open the throttle and peer back in with a light. That black is from the fuel injectors and all the charge not being drawn in at shut down.
My Harley and my Yamaha with over 50K still have fairly clean intakes. Now I have see Harley with a lot of overlap in the valves or worn cylinders and that have black intakes from blow by and the little spit back at idle. However, a lot of this is simple from the fuel injectors just reward of the air butterfly.
My Yamaha actually has a drain hose on the bottom of the air box. However, it turn a 1000 rpm more then the Harley at interstate speed and generates a lot more oil out the breathers.
I only posted my opinion since you ask and I figured you may be unaware of the Federal 10K fine. Not sure who it applies to however. My local state inspector required here in VA actually checks for it with a light and mirror. I ask him one day what he was looking for and he just smiled.
Last edited by Jackie Paper; Jul 7, 2016 at 10:52 AM.
If I understand this "fix" of routing the bypass oil outside the airbox...isn't it now going to drip and "spray" onto anything downwind in its path (back rim, rear fender, exhaust pipes, etc.) or worse a nasty oil spot on the garage floor when you park the bike?
Yes it will drip on the floor. Reason I mentioned wanting catch can. most of what comes out it is hot moist air. After I rebuilt the top end in two hundred miles the tops of piston was black already. Why I had to get that stuff out of air box. These bikes have a sad head design (bath tub). This is a problem with carbon because of the front and back being a dead spot so to speak, carbon builds up there and hits the piston. I run Lucas injection cleaner to keep pistons clean as u still get build up with vent mod but not near as nasty.
Sorry I have no pictures at the moment. But I can tell you that the picture where AlbertG drilled a hole where the tube is located in the airbox is where I put my breather filter in.
After checking it after a 1000 plus miles it definitely works. The breather filer is definitely catching some oil. If you think about it, it is the same concept as putting the breather tube directly onto the stock air filter, except you are using an extra filter.
Just buy one of these on ebay or go to the autoparts store and find one for 5 bucks. Also find a step up barb hose fitting that attaches to the tube and the breather.
I was all set and in fact ordered a kit with a catch can, to vent my 2010 crankcase externally. Then recently at a local meet and greet a well known tuner reiterated what I heard here for the first time. It will cause the Umbrella flaps to flutter which will create a host of other issues. His opinion is that a properly running and maintained engine will never create enough blow-by to do any harm. The motor is designed to vent as it does to meet EPA standards hence the system needs to stay intact to work as designed? Since this type of venting is a Federal mandate Harley designed it to work and modifying it will just create a problem down the line because of the Umbrella valve flutter? What that might be I really don't know. Since I have literally no oil in my air cleaner I'm going to leave well enough alone for now till I can get more definitive answers.
Good idea. This subject has been beaten to death and it seems that the main concern people have is carbon build up on the pistons from oil bring introduced into the combustion chamber and hot air from the crank case. If your crank case is over filled, you probably will get oil in your air cleaner as well as in the combustion chamber but very little if any. The amount hot air they talk about is so small that I highly doubt it could be measured as far as performance.
I have never had as much as one drop of oil on the air filter or the intake.
I'm not sure how anyone can assume that an oil mist will exit the head and be deposited in the air filter without entering the vacuum of air entering the intake. Take a look at the angle of the air channels as they enter the breather, They are aimed at the intake by design. By the EPA's design that is. The oil doesn't come out of those holes in tiny cold droplets to fall to the bottom of the air filter housing, it's a hot fine mist of air and oil and it will and does enter the combustion chamber and eventually build up on the heads and the tops of the pistons. It is more of a problem on modified bikes than stock bikes but it happens to both. I see stock bikes that do long hi-way rides start to have dripping air filters after 30,000 or so miles. Low mileage bikes and those that bar hop/short trip may never have an issue but long distance high mileage bikes do stock or otherwise.
Just my opinion of what I have seen and experienced.
Why couldn't you make a tini venturi at the drain end of the line, so as you rode, you created a negative pressure and get rid of all the junk? Maybe a model airplane throttle body with a venturi inside, or a small motor carb venturi, or make your own? Just thinking out loud here.
I have a stock '14 RK with stock AC. I just did the AC/TB bypass but haven't had a chance to ride the bike yet after this mod...this is my only mod to date. I checked the throttle body a couple times approx. 4K miles after an oil change. I definitely had an oily film throughout the throttle body, and especially at the bottom edge of the stock AC (which is a dry filter unit that gets a warm-water/dish soap cleaning and thorough drying with each oil change). So I know that my bike is getting oily mist in the TB. I don't get any oil collecting in the AC housing or dripping anywhere.
I've been very careful when adding oil during an oil change. I add 3 qts...run the bike to fill the filter and then check level again. I've checked the level both hot and cold, and both on the Jiffy stand and upright on a jack. I keep the level about midway on the dipstick...never "full" on the dipstick. I end up adding approx 3.3 qts of oil after an oil/filter change. My point is, I don't think I am overfilling the engine however I still get oily residue in the TB and the stock filter cartridge. I don't run the bike extremely hard (2,200 - 3,500 RPMs most of the time with an occasional 4K RPM burst), but I don't baby it either...and my riding is a mix of highway and rural cruising.
I know it's not being overfilled with oil...but my TB is still getting oily. So yes, I am concerned about this oil going into my TB. That can't be good for the motor over time/miles. Just my .02.
After all this discussion I'm not sure what I'm going to do regarding keeping the bypass in place. I try to be environmentally conscious. However, I'm hard-pressed to believe that MCs with by-passes are contributing to global pollution to any significant degree.
Without knowing the finer points of this debate regarding flutter, etc. I ran an external breather with a catch can on my RK. My observation after 1,000 miles is the motor runs better/smoother and has more pep on the throttle. Been ridding a long time and don't consider myself susceptible to placebo effects regarding mods. If anything I usually worry I'm screwing it up somehow. In this case however I'd say there was a noticeable performance gain.
Last edited by Thingfish; Jul 7, 2016 at 07:00 PM.
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