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Discussion Starter #1
I see this all the time on all forums
"oil level too high,oil coming out of the air filter"
Can anyone explain why this should be,or is it another myth?
 

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I see this all the time on all forums
"oil level too high,oil coming out of the air filter"
Can anyone explain why this should be,or is it another myth?
Too much oil can increase the pressure on the crankcase ventilator in the heads, which causes the excessive oil to blow out the breathers, which drain into the air cleaner.

The Crankcase Breathers are meant to allow excessive AIR pressure in the crankcase to be vented into the intake. The excessive air pressure comes from the movement of the pistons. There are vents in the heads, and a valve, called the umbrella valve (because it looks like an umbrella) that allows the pressure to bleed into the intake. When there is too much oil, it makes it's way past the umbrella valves into the intake, saturating the filter, and leaking thru into the ham can, onto your leg, the exhaust pipes, the saddle bags, and making an all around mess of things.
 

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Discussion Starter #3
Too much oil can increase the pressure on the crankcase ventilator in the heads, which causes the excessive oil to blow out the breathers, which drain into the air cleaner.

The Crankcase Breathers are meant to allow excessive AIR pressure in the crankcase to be vented into the intake. The excessive air pressure comes from the movement of the pistons. There are vents in the heads, and a valve, called the umbrella valve (because it looks like an umbrella) that allows the pressure to bleed into the intake. When there is too much oil, it makes it's way past the umbrella valves into the intake, saturating the filter, and leaking thru into the ham can, onto your leg, the exhaust pipes, the saddle bags, and making an all around mess of things.
The oil is stored in the oil tank/sump and not in the crankcase,how does this affect the pressure in the crank case?
 

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The complete oil system is under some pressure also the oil will expand some, that is why you are suppose to check the oil when hot while the bike is on the jiffy stand for a accurate oil reading according to HD instructions. Also as the oil flows through the oil tank/sump it creates a turbulence which results in higher oil level in the sump, That is why you only check the oil when the bike has been turned off for 3to5 minutes for a accurate reading. When the oil is overfull it has to vent someplace and on our bikes HD put the vent in the intake.
 

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Our motors hold 4 quarts dry. Meaning never had oil in it. You will retain nearly 1/2 quart after an oil change. Some in the sump, in the cam chest, gallerys, etc. If you put 4 full quarts back in after a change then by fault you have over filled by approx. 1/2 quart. That's what winds up in the filter media.
 

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Discussion Starter #6
The complete oil system is under some pressure also the oil will expand some, that is why you are suppose to check the oil when hot while the bike is on the jiffy stand for a accurate oil reading according to HD instructions. Also as the oil flows through the oil tank/sump it creates a turbulence which results in higher oil level in the sump, That is why you only check the oil when the bike has been turned off for 3to5 minutes for a accurate reading. When the oil is overfull it has to vent someplace and on our bikes HD put the vent in the intake.
Surely the amount of oil remains the same in the engine crankcase because the oil is constantly removed by the scavenge pump, regardless of how much oil is in the oil tank/sump
 

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Discussion Starter #7
Our motors hold 4 quarts dry. Meaning never had oil in it. You will retain nearly 1/2 quart after an oil change. Some in the sump, in the cam chest, gallerys, etc. If you put 4 full quarts back in after a change then by fault you have over filled by approx. 1/2 quart. That's what winds up in the filter media.
I'm not asking how people change their oil,how they change it is immaterial,
if people do it the way you suggest they are doing it wrong, and that doesn't explain how the excess oil gets from the oil tank/sump to the air filter.
 

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Come on Bigtrev8xl. You've received answers to your question plus some related potential causes.

Take it easy man. Please consider that your responses make is seem as though you have already determined that those answers and causes are myths.

Surely you wouldn't already know more about the way things work in a Harley engine and oiling system than the folks who are trying to offer answers or you wouldn't have asked the question in the first place.
 

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Now for my answer to your question:

Modern EPA regulations are complied with by venting hot engine gasses and the related pollutants into the intake rather than directly to the external atmosphere. Any oil, even in vapor form, that gets into that venting system is therefore often carried into the intake along with those hot gasses.

The main objective is to either burn pollutants during combustion and let the Catalytic Converter handle the residue or "re-breathe" them by re-routing them back into the engine.

However, if the crankcase of a wet-sump type engine is filled with oil far enough so that oil level intrudes into an input for the venting system, then that issue is quite apparent since the air cleaner can become saturated. Hence, "...oil coming out of the air filter".
 

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Discussion Starter #11
However, if the crankcase of a wet-sump type engine is filled with oil far enough so that oil level intrudes into an input for the venting system, then that issue is quite apparent since the air cleaner can become saturated. Hence, "...oil coming out of the air filter".
But Harleys are a dry sump engine
 

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Have you ever gotten the puff of smoke right out of the air filter upon starting? Does that relate to the too much oil your talking about?
 

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Discussion Starter #13
Come on Bigtrev8xl. You've received answers to your question plus some related potential causes.

Take it easy man. Please consider that your responses make is seem as though you have already determined that those answers and causes are myths.

Surely you wouldn't already know more about the way things work in a Harley engine and oiling system than the folks who are trying to offer answers or you wouldn't have asked the question in the first place.
Wouldn't I.
 

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Discussion Starter #16
Have you ever gotten the puff of smoke right out of the air filter upon starting? Does that relate to the too much oil your talking about?
Not seen seen it on this EFI bike,used to see it on carbed bikes.
 

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It's not a myth that they leak oil from the oil filter,they all do that, from my first Sportster,but how does decreasing the oil level in a wet sump engine stop it.
Just the filter! Ever have a Norton? ...or live with Lucas, God of Darkness (maybe do as I did and replace everything except the alternator). Disassemble and replace all gaskets.

Don't get me wrong, I LOVED my old Norton and clobbered a ton of Honda 750s - either on the road or at the drags. Oops... I digress. Show me your tool chest full of Whitworth spanners.
 

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I'm not asking how people change their oil,how they change it is immaterial,
if people do it the way you suggest they are doing it wrong, and that doesn't explain how the excess oil gets from the oil tank/sump to the air filter.
Thru the umbrella valves
 

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Now for my answer to your question:

Modern EPA regulations are complied with by venting hot engine gasses and the related pollutants into the intake rather than directly to the external atmosphere. Any oil, even in vapor form, that gets into that venting system is therefore often carried into the intake along with those hot gasses.

The main objective is to either burn pollutants during combustion and let the Catalytic Converter handle the residue or "re-breathe" them by re-routing them back into the engine.

However, if the crankcase of a wet-sump type engine is filled with oil far enough so that oil level intrudes into an input for the venting system, then that issue is quite apparent since the air cleaner can become saturated. Hence, "...oil coming out of the air filter".
This.

Hmmm, perhaps the OP could relate to the PCV system of their cage? If you check the PCV valve or, in some cases with V design engines you have a PCV valve on one valve cover and a vent line to the intake (between the air filter and the throttlebody) on the other. They typically are full of gunk and maybe minute parts of liquid from oil vapor.
The vent line on your cage is probably similar to to the harley design where the crankcase is vented to the intake (where there is a vacuum when running) to keep that nasty crap out of the atmosphere.
And it is nasty crap. Valve stem seals and such are not perfect. Combustion gasses escape into the crankcase because the heads have to allow the oil to drain back to the crankcase and these gasses can cause a positive pressure in your crankcase. These gasses have to go somewhere. I am not intimately familiar with the twin cam design but it appears that the venting distance from the crankcase/sump to the air filter is short enough that in a typical situation when the gasses would be sucked into the intake it is possible to suck the actual oil along the same path if the oil level in the crankcase is high enough and you have enough foaming from the movement of oil.
On your bike the air filter sits right on top of that vent path. Any residule oil could end up in the air filter.
 
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