Here you go... some of these have already been posted, but here they are all in one place.

 

Like someone else posted, venting the oil back into the intake is just hiding a root problem isn't it? What adverse affect can it have since that oil is now being sucked into the cylinder? Maybe none, but it doesn't seem quite right to me. Luckily for me, I only notice a small oil film on top of the case directly beneath the breather. When I pulled the breather off (SE Heavy Breather) I noticed some oil build up on the bottom, but not enough to get on boots, bags etc.. I would just like to stop even the little bit. Routing the tubes may be the most economical way, but is it really the correct way?

 

There are primarily two schools of thought as far as re-routing the breathers go. Both have been discussed in this thread. One is to route the breathers externally to atmosphere. The other, which I have chosen, is to re-route the breathers within the air cleaner/throttle body. Either will work and each have their own pros and cons.

Many will argue that oil being introduced to the intake system will cause carbon build-up in the combustion chamber and these folks are more likely to select the vent-to-atmosphere option. I don't disagree with this position but I do question how big of an issue the carbon build up actually is. Afterall, this is the way the system is designed to work originally.

The primary reason for this design is for emission control, so that crankcase vapors are burned during the combustion process rather than simply being vented to atmosphere. But another benefit of this design that rarely, if ever, gets mentioned, is that the low-pressure condition created within the air cleaner/throttle body actually helps purge vapors from the crankcase. This is known as positive crankcase ventilation and reduces the amount of crankcase and oil contamination caused by combustion by-products reaching the crankcase.

As for the cause, or causes, it’s a combination of crankcase pressure, air cleaner breather port design, in-head breather design and function, and cylinder head oiling and return. I'm going to address the first two listed causes.

There will always be some amount of crankcase pressure, this is perfectly normal. But excessive crankcase pressure will cause the issue being discussed in this thread. Where the excessive crankcase pressure is coming from is the real question (rings, valves, head gaskets, piston stroke etc.). The higher the crankcase pressure, the more air will need to flow through the breathers. The more airflow through the breathers, the more oil mist and other combustion by-products it will carry.

The oil mist and other combustion by-products have to go somewhere. When the breathers are vented to atmosphere, that’s exactly where they go, to the atmosphere or to a catch can if one is installed. When vented to the intake system, the intended result is that they will be burned with the fuel during the combustion process.

I say “intended result” because the design relies upon the crankcase ventilation products to be ‘sucked’ into the combustion chamber. With many aftermarket air cleaner designs, the breather port location does not accomplish this effectively in all cases (considering the other potential causes noted previously) and the end result is oil in, or leaking out of, the air cleaner.

Of all of the potential causes, the easiest one to address is the air cleaner breather ports. That’s why the majority of the suggested fixes in this thread recommend re-routing the breathers – either externally to atmosphere or internally within the air cleaner/throttle body.

 

I think the real problem is the drain back holes are too small and the sponges in the breather assembly are on the rocker support plate...which causes the breather sponges to get saturated with oil and the pressure from he crankcase gasses going through the sponge also blows liquid oil through to the air cleaner...routing into the intake does cause carbon build up and it can be a significant amount...enough over a period of time that the chance of detonation and run on can happen...
Harley has come out with a new breather assembly which leaves an air gap between the rocker plate and the sponge(which is also denser) so the oil/air mix has a chance to separate and the oil drains back to the bottom and only air blows through the sponge and into the air cleaner/intake which is what's supposed to happen...enlarging the drain back holes also allows the oil to return a little faster to lessen the chance of the breather sponge to become saturated with oil which is the reason why oil is blown out of the vents...

 

Have to ask. Why additional pressure in the crankcase running the oil at the recommended level? Seems the MoCo would have addressed this issue. I no longer have this problem with either of my Twinkies but both have AR big suckers on them. I did find that the runners that the oil is supposed to follow back into the engine had castings left at the end of the channels and all I did was remove it witha Dremel to solve the drip.

 

Yes and there are HD TT411a and TT411b bulletins on how to address a customers oil carry over complaints. One fix is the larger oil drain back hole. One of the others is to make sure the breather bolts have been installed unmolested as many guys drill out the breather bolts thinking they are helping venting but they are only giving the oil an easier route into the intake area. They also give a very clear visual diagram on oil levels hot and cold. It is available online(just not here)

 

I've vented the blow by into the throttle body 20,000 miles ago with no adverse effects yet. No more oil down the side of the bike or dripping out of the air cleaner. I've running a K&N RK-3910. Here's some pictures, one at 20,000 miles the second at 40,000 miles.

 

"The primary reason for this design is for emission control, so that crankcase vapors are burned during the combustion process rather than simply being vented to atmosphere. But another benefit of this design that rarely, if ever, gets mentioned, is that the low-pressure condition created within the air cleaner/throttle body actually helps purge vapors from the crankcase. This is known as positive crankcase ventilation and reduces the amount of crankcase and oil contamination caused by combustion by-products reaching the crankcase. "


Damn, my car has a PCV Valve. Why didn't they put one on my bike. That would cure everything.

 

If I remember the PCV design of automobiles is theres a check valve that wont allow anything solid to be ingested. Its placed on the valve cover and routed to the intake base with a hose fitting. If the MoCo would put a PCV on each valve cover then route it to the intake in a similar fashion this convo would not be taking place. No kuriakyn has an air filter with an aluminum sleeve between the air filter plate and the TB where the hoses from the jugs route to placing the PCV right where automobiles put them.....

 

Heres what Im talking about....pull up the instruction sheet:
http://www.kuryakyn.com/Products/3835/Street-Sleeper