You my dear sir need to read the service manual on the oil system. I did not make this up. The vent is the top vent to allow oil to be drawn out the bottom. True, the vent from the crankcase like you say is an emission related item that goes into the air filter body. Since I have been walking all over the FP's post, I will gather the pictures and be brief . May post a new thread on internal and external vent and breather systems.

This is for a Softail

Note the Vent line coming off the top which is where excess oil would go if it did not pop the dipstick out. From there it goes to a cross drilled passageways that makes two 90 degree turns and goes into the top of the transmission open cavity. Note attachment 3 especially the last paragraph.

Will add the face of a softail transmission as soon as I find it for the port in it.
Will do the Dyna/Cruiser shortly

One of the biggest reason the primary and oil bag use the transmission vent which is a simple open downtube is the fact that to vent them to the engine compartment would require some type of valve system since the engine crankcase is itself under pressure and at certain times under a vacuum.

 

Thanks, I have many times, and studied it once again just before posting.

Your attachments show and describe the oil tank vent line connecting to the cam chest area near the rear lifters, just as I previously described. Not to the transmission.
Text from your third attachment:
"note that a third hose (4) clamped to a fitting behind the rear lifter cover connects the cam compartment with the oil tank via a third drilling in the transmission case. This crankcase breather connection provides the pressure balance necessary for oil circulation."

This drilling in the transmission case refers to a passageway contained within the walls of the case, not one which connects to the interior of the transmission. Perhaps that is where you're getting confused.

The primary uses the transmission vent, the engine oil reservoir does not. No valve system is required between the engine and the oil reservoir to damp the pressure pulses, because the small size and the length of the vent passages damps the pulses sufficiently.

 

You are correct..the upper statement was what confused me. I check a Softail 5 speed transmission that I thought had a vent hole thru the long cast recess between the two upper mounting holes and it does not. Thanks for bearing with me and getting me straight.

 

Hey, I felt bad about disagreeing with you, because you typically post solid stuff.

I'm the one who usually gets major crapola, challenging old wives tales as I tend to do, like ethanol-containing fuel being bad, and tuning being needed for Stage 1 mods (on newer fuel-injected bikes), or they'll melt down or blow up and chit.

 

Well I'm glad that post #31 has gotten so much attention and I hope that softails will stop being brought up in a Dyna thread, especially considering the differences in oil containment.

DK Custom's piston pics are exactly what mine looked like after about 8K miles with the stock breather setup. Bad buildup, knocking... I re-routed mine to an external filter hanging under the transmission and with some engine cleaning additives, my piston tops are starting to clean up. Oily air should never be and was never intended to be routed into the combustion chamber of any engine. This is EPA bullshit that doesn't lessen global air pollution one iota.

 

Amazing isn't it?

 

Just in case you missed it, the topic was about oil breathers, and I criticised that recommending that oil levels be intentionally underserviced in order to minimize excessive oil from coming from the breathers and that doing this could cause problems from overheating. Our Harley Davidson engines are air cooled engines, and air cooled engines are engineered to use oil for cooling as well as lubrication. This is a fact.

I do not know all the engineering parameters and quirks of the twin cam powertrain. I do not know where the breakdown temperature parameters are, I do not know what the most likely component to fail from overheating is, and I do not know what the best oil to use in this engine is. But, I do not have to guess because Harley Davidson provides me with this information. Harley Davidson also specifies acceptable oil blends and types, change intervals, and clear and precise directions to keep the oil at a certain level. I also do not know the cooling coefficient of the different blends of oil and therefore cannot calculate what cooling from the oil is provided by the design of the engine and the cooling effect of the oil on that design. All this engineering stuff gets complicated as I learned a long time ago in A&P school. So, if you do not know this, then how can you say with all certainty, and understanding that if you are wrong that the consequences can be catastrophic, that oil level is not critical when MoCo says it is??

Maybe it is the airplane mechanic in me that makes me so **** about following manufacturers guidelines and requirements to the letter. Could be that little voice that for years told me that if I screwed the pooch, someone might die. Maybe that is why I do not take stupid risks when it comes to maintaining my Harley and would never intentionally recommend anyone ignore manufacturer's servicing requirements. That is irresponsible.

Now, this is where I take on your role from above. MoCo says to keep a tender on the battery. Battery manufacturers say don't. (even though battery manufacturers make tenders and HD will not warranty a battery failure, even if a tender is used...see the connection ) My disagreement with this practice is based on formal training and years of experience. Even if you don't agree, not using a tender will not cause a catastrophic engine failure like low oil levels will. About once a month, a topic comes up where someone who doesn't ride often has to replace their battery even though they kept it on a tender...folks, there is a connection.

I guess if you are one of those 500 miles-per-year riders and would rather keep it looking pretty in the garage instead of out on the road, you probably need someway to keep the battery charged. I ride mine...a lot...that's why I bought it...it don't need a tender.

 

Just in case you missed it , no one has recommended that oil levels be "underserviced", or run below the recommended range. The advice was that the oil level be run somewhere near the middle of Harley's recommended range.

 

Exactly. No one told anybody to run below the add line. And according to the manual, the middle of the range is exactly where it should be kept.

 

I was an aircraft mechanic as well, as I've told you before, but I'm not going to get into a long drawn out conversation about such a stupid topic. The point of this thread is that venting crankcase emissions to the atmosphere vs into the combustion chamber is indisputably better for the engine. I'll bet you've never seen a piston aircraft engine that routes crankcase vapors to the intake.

Oh and the reason the moco recommends the tender on the battery all the time is they know about the heavy parasitic current draw these bikes have. The battery manufacturer doesn't know what bikes their batteries are going into, so of course they aren't going to state that you should have to keep a tender on them all the time. And it's not that you HAVE to keep a tender on it every day, the point in that thread was that keeping it on all the time wont hurt the battery at all, which is 100% true if you have a properly working smart tender. Your statement that sometimes batteries still die even when kept on tenders is a worthless correlation because all batteries eventually die. Now if you have proof that those batteries died BECAUSE of the tender, post it up, chief.