94 evo
Road Master
Joined: May 2007
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Run the two head breather hoses to a tee-fitting then to a single hose that goes to the ground. If you're Green use a canister to catch the oil. There are other things like "beehive" fittings but those eventually leak too.
What you're looking at is blowby (oil & condensed water) from the heads. When the MOCO finally sealed the oil leaks in the EVO the blowby oil (and what to do with it) was something they couldn't fix without a major re-design of the oil return system. So they just ran hoses from the rocker boxes to the intake system. The idea being the blowby would be ingested by the carburetor and burned up in the cylinders. The problem is who wants all that waste oil and water (which forms a milky white sludge) gumming up your intake system, and as you have seen, it doesn't work that well anyway.
What you're looking at is blowby (oil & condensed water) from the heads. When the MOCO finally sealed the oil leaks in the EVO the blowby oil (and what to do with it) was something they couldn't fix without a major re-design of the oil return system. So they just ran hoses from the rocker boxes to the intake system. The idea being the blowby would be ingested by the carburetor and burned up in the cylinders. The problem is who wants all that waste oil and water (which forms a milky white sludge) gumming up your intake system, and as you have seen, it doesn't work that well anyway.
Last edited by NickD; Jul 8, 2011 at 01:43 PM.
Seasoned HDF Member
Joined: Jun 2010
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From: Upstate New York
Back in the day, the Harley was vented from the timing case, and the tube just exited onto the ground. One day the mighty EPA looked at that arrangement and said "that just won't do!" and decreed that henceforth, all Evos from '93 and up would breathe through the heads, where all that nast stuff would get burned by the engine (hopefully). You can see how well that idea worked.
Road Master
Joined: May 2009
Posts: 1,232
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From: Powder Springs, GA
Back in the day, the Harley was vented from the timing case, and the tube just exited onto the ground. One day the mighty EPA looked at that arrangement and said "that just won't do!" and decreed that henceforth, all Evos from '93 and up would breathe through the heads, where all that nast stuff would get burned by the engine (hopefully). You can see how well that idea worked.
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Stage IV
Joined: Jul 2011
Posts: 4
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From: indiana
I didn't know that is why they changed it but I do know it does nothin but make a mess of my motor
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Seasoned HDF Member
Joined: May 2008
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From: South Carolina
One day the mighty EPA looked at that arrangement and said "that just won't do!" and decreed that henceforth, all Evos from '93 and up would breathe through the heads, where all that nast stuff would get burned by the engine (hopefully). You can see how well that idea worked.
An engine with 2 pistons going up and down at nearly the same time is always going to have some oil in the breather system unless you add some type of air oil separator, like a well designed catch can...
The breather system used before the head breather did not vent overboard, the hose ran from the crankcase up to a fitting on the back of the carb backing plate. That system was just as messy, if left intact.
The head breather system eliminated the external plumbing from the crankcase to the carb backing plate. It also is a little more difficult to modify, which may be the reason for the head breather.
I think if you must keep all the oil onboard, the air oil seperating catch can is the best way.
Last edited by Dan89FLSTC; Jul 8, 2011 at 08:58 AM.
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Joined: Jun 2010
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From: Upstate New York
Yes, my simplified explanation left out the intermediate step of venting the case breather into the air cleaner. That system was, of course easier to deal with. It was a simple matter to re route the breather hose. The head breather is a bit more complicated, and you have to either live with a "well oiled" air cleaner, or put up with unsightly drain lines.
I use a Ness "big sucker", and, despite the vents exiting by the carb intake, I still get oil dripping off the bottom of the air cleaner. I fold up a paper towel and stuff it between the air cleaner and the cover. It seems to soak up about a teaspoon of oil every 500 miles or so.
I use a Ness "big sucker", and, despite the vents exiting by the carb intake, I still get oil dripping off the bottom of the air cleaner. I fold up a paper towel and stuff it between the air cleaner and the cover. It seems to soak up about a teaspoon of oil every 500 miles or so.
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