I really don't know why some guys are putting a filter on the breather. Vapor is expelled through there and cannot go the other way due to the umbrella valves in the rocker box; air cannot go up that tube. All the filter will do is catch the oil until it gets saturated enough and then it'll start dripping too. Also, it restricts the flow of the crankcase vapors and since vacuum from the intake is no longer pulling the vapors out, it passively vents so you really don't want any restriction at all.....unless I'm completely missing something. I just ran my breather tube down behind the transmission with no filter and it dumps to the ground.
I ran mine to frame rail and open pointed to the ground without a filter. Recent startup for quick ride and it shot a visable light mist pattern on the floor. Thats not good going to the intake or to a filter media
Last edited by GregGillette; 02-23-2017 at 04:47 PM.
I really don't know why some guys are putting a filter on the breather. Vapor is expelled through there and cannot go the other way due to the umbrella valves in the rocker box; air cannot go up that tube. All the filter will do is catch the oil until it gets saturated enough and then it'll start dripping too. Also, it restricts the flow of the crankcase vapors and since vacuum from the intake is no longer pulling the vapors out, it passively vents so you really don't want any restriction at all.....unless I'm completely missing something. I just ran my breather tube down behind the transmission with no filter and it dumps to the ground.
I happened to see the filter at AutoZone and thought it would look good on it.
I've been running it since I went to the 107" a couple years ago and have only cleaned the filter a couple times....no drips at all.
I seriously doubt the filter creates much, if any restriction.
Here is my bypass done when I added the K&N, and keeping the stock cover.
A small plug to close the hole where the breather would normally go.
[I] Then took a 5/16 hose to snuggly fit over the air cleaner tube and placed a 1/4 to 1/2 barbed union about halfway down, and attached a piece of 3/8 to fit over the breather inlet which is placed at about the 5 o'clock position on the air box.
Here is my bypass done when I added the K&N, and keeping the stock cover.
A small plug to close the hole where the breather would normally go.
Looks good. I too went with a K&N filter and kept the stock cover. Can't see the breather hoses hardly at all. I had the SE intake with K&N but pulled it off because it was too loud. No decrease in performance either.
It seems like most folks who bypass their breather do it because of the oil drip. In that case, I could see the justification. That is annoying. But I have never heard of an engine failure or any other issue, besides oil drips, that could be tied to the breathers allowing oil vapors to be consumed by the engine.
Most Harley's, or any other motorcycles, will not see 100,000 miles with out some sort of engine work. Mostly due to folks getting bored with just riding so they have to touch something or spend money to impress their buddies. Cars also experience a degradation because of the oil breather into the engine, but is is offset because of the additional cylinders. So it is not noticed as much.
A lot depends on how you ride your Harley. My bike frequently sees 5000 RPM. I usually shift at 4000-4500, like when merging onto a freeway. So I create more vacuum for longer periods than someone who shifts at lower RPMs. So, is the breather bypass necessary? Probably not. A bypass cannot hurt the motor. But over time, the oil mist can harm the motor.
Most Harley's, or any other motorcycles, will not see 100,000 miles with out some sort of engine work. Mostly due to folks getting bored with just riding so they have to touch something or spend money to impress their buddies. Cars also experience a degradation because of the oil breather into the engine, but is is offset because of the additional cylinders. So it is not noticed as much.
A lot depends on how you ride your Harley. My bike frequently sees 5000 RPM. I usually shift at 4000-4500, like when merging onto a freeway. So I create more vacuum for longer periods than someone who shifts at lower RPMs. So, is the breather bypass necessary? Probably not. A bypass cannot hurt the motor. But over time, the oil mist can harm the motor.
True. Breather bypass is sort of an OCD thing and I'll be the first to admit it; just put a catch can on my new truck and it already caught about a tablespoon of oil after 100 miles....probably a good part of it is condensation. But you'd actually be pulling LESS vacuum at those RPM's you're running.
02-23-2017, 04:44 PM
Nice ride!
