Puking oil through the Air Filter
Road Captain
Joined: Oct 2008
Posts: 699
Likes: 391
From: Fellows. WI
All engines produce oil mist. There's no way around it. Your daily driver produces oil mist, your lawn mower produces oil mist, the diesel powered truck that hauls groceries to your local supermarket produces oil mist.
The intake tract and combustion chambers of my ol' Harley are nice and clean because I vent the oil mist outside the AC. The right side of my bike is free of oil and the dirt it catches.
I had some fun that catch can, too.......
If the thought of having a vent hose and catch can hanging off your bike offends you, by all means, continue venting the heads as Harley designed.
If you don't mind cleaning the oil off the AC backing plate, the IAC plunger and bypass, and changing/cleaning your air filter at least once a year, by all means, continue to do so.
If cleaning dripping oil off the AC cover, the lifter blocks, cam chest cover and the right side of your bike is an enjoyable task, carry on.
The choice is yours.
Last edited by orbit; Mar 5, 2020 at 06:43 PM.
HDF Community Team
Joined: Mar 2017
Posts: 7,825
Likes: 4,383
From: Texas
Mmm I don't think so. The path of least resistance will be the umbrella vents (it's easier for the pressure to escape the breather vent than it is to push the oil out of the way and escape out the vented dipstick.
Road Captain
Joined: Aug 2018
Posts: 587
Likes: 312
From: here n there
Amazing that a company that has been designing and building engines for 117 years can't figure out how to manage a crankcase breather system. Literally no other motor company on the planet is so befuddled by this simple problem.
Seasoned HDF Member
Joined: Jan 2008
Posts: 13,621
Likes: 11,354
From: State of Confusion
probably has something to do with stubbornly clinging to the archaic design because of looks, sound, heritage, whatever...the VROD was an example of what they are capable of..people just still love these bikes and don't want too much change but they certainly could do better at some things
Seasoned HDF Member
Joined: Aug 2011
Posts: 11,814
Likes: 5,120
From: SW Ohio
I'm the first one for calling out HD on a poor job but the crank case vent system isn't their fault. The EPA mandates that excess pressure/oil mist be routed to the intake for "combustion". All anyone needs to do is route the breathers to two hoses, down to a T fitting and then one hose to the ground. There's no need for a filter as the umbrella valves are one way and there's no need for catch can. Actually, a catch can (depending on design and size) can impede pressure ventilation. As a side note, HD big twins have pistons the size of small paint cans which pretty much rise and fall at the same time. This creates a LOT of crankcase pressure.
Whether you decide to do this mod or not, the engine (and how the bike is ridden) will determine the oil level. Putting in more than that is at the very least wasteful and messy, at the very most pumping more oil into the intake/cylinders to be cooked onto the piston tops. Once that sh*t is caked on good it can super heat faster than the piston material itself and cause pre-ignition. Look that one up, its expen$ive.
In my opinion, kibbitzing about what cleaner/wax to use or what chrome gee gaw cover to buy next should all be secondary to venting the crank case to the ground.
Whether you decide to do this mod or not, the engine (and how the bike is ridden) will determine the oil level. Putting in more than that is at the very least wasteful and messy, at the very most pumping more oil into the intake/cylinders to be cooked onto the piston tops. Once that sh*t is caked on good it can super heat faster than the piston material itself and cause pre-ignition. Look that one up, its expen$ive.
In my opinion, kibbitzing about what cleaner/wax to use or what chrome gee gaw cover to buy next should all be secondary to venting the crank case to the ground.
Last edited by Campy Roadie; Mar 6, 2020 at 06:09 AM.
HDF Community Team
Joined: Mar 2017
Posts: 7,825
Likes: 4,383
From: Texas
probably has something to do with stubbornly clinging to the archaic design because of looks, sound, heritage, whatever...the VROD was an example of what they are capable of Porsche could do for Harley..people just still love these bikes and don't want too much change but they certainly could do better at some things
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Tourer
Joined: Jul 2019
Posts: 308
Likes: 39
From: So Cal Lower Desert
probably has something to do with stubbornly clinging to the archaic design because of looks, sound, heritage, whatever...the VROD was an example of what they are capable of..people just still love these bikes and don't want too much change but they certainly could do better at some things
Bottom line here is if it doesn't brake it doesn't make them money!