What causes excess oil into intake on a new rebuild?
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Grand HDF Member
Joined: Dec 2007
Posts: 4,999
Likes: 55
From: Bay Area
What causes excess oil into intake on a new rebuild?
Can anyone explain why some motors will bleed excess oil thru the intake and others don't? I have a new build and am using oil at the rate of 4 quarts in 3500 miles. If I run the breathers to the ground I don't use oil I've just installed an Arlen ness filter per recommendation from the builder to stop the issue. Well it doesn't work.
Any info from the forum? I'm about to call the builder but he is good at bs'ing and would like to be more informative when I call.
I suppose I could vent to the ground but that just doesn't seem like a fix but more like a band aid.
I'm a mechanic by trade but not a HD wrench, I think I have somewhat of an understanding of how the breather system works. Maybe I am missing something.
As a note on a compression check I have 200 front and 190 in the rear. If 10% variance may be the norm on a 8 cylinder would that be acceptable on a. Twin.
Thanks forum members!
Any info from the forum? I'm about to call the builder but he is good at bs'ing and would like to be more informative when I call.
I suppose I could vent to the ground but that just doesn't seem like a fix but more like a band aid.
I'm a mechanic by trade but not a HD wrench, I think I have somewhat of an understanding of how the breather system works. Maybe I am missing something.
As a note on a compression check I have 200 front and 190 in the rear. If 10% variance may be the norm on a 8 cylinder would that be acceptable on a. Twin.
Thanks forum members!
Ultimate HDF Member
Joined: Mar 2012
Posts: 6,129
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From: Santa Cruz
Could be something out of wack with A/C install but I'd still bet on bad beathers/install.
Tourer
Joined: Sep 2007
Posts: 415
Likes: 13
From: Northeastern Md.
A new/rebuilt (or better put-new rings) engine is going to have a lot of crankcase pressure and vapor because combustion pressure leaks past the rings/cylinder walls.When the breathers are routed to the intake,vacuum from engine is going to pull that excess amount of vapor through the intake.Breathers to atmosphere aren't going to route the vapors through the intake.As engine "breaks in" (rings seat) the crankcase pressure will reduce,as combustion will be reduced from leaking past the rings into the crankcase.How many miles are on your engine?
Last edited by Am4wag; Nov 9, 2013 at 11:12 AM.
Thread Starter
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Grand HDF Member
Joined: Dec 2007
Posts: 4,999
Likes: 55
From: Bay Area
That's kind of what I'm thinking the reason for the ac change from the SW snorkel he says was causing a positive intake psi and holding the umbrella valves open. My next thought is the rings didn't seat right or he didn't space the ring gap properly. I don't ha e a power loss though
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Grand HDF Member
Joined: Dec 2007
Posts: 4,999
Likes: 55
From: Bay Area
Between 6-7k. I just had an oil sample done and the only elevated thing was aluminum at 31 ppm which they say is acceptable for break in. Which at that time had 4600 on the motor and 3500 of it was 70-95 mph for 12 days at 8 hours almost a day.
Elite HDF Member
Joined: Sep 2007
Posts: 4,928
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From: Near Myrtle Beach, SC
Vent to the atmosphere and forget abt it. As stated, its the neg pressure sucking the oil thru the breather tubes.
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Thread Starter
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Grand HDF Member
Joined: Dec 2007
Posts: 4,999
Likes: 55
From: Bay Area
A new/rebuilt (or better put-new rings) engine is going to have a lot of crankcase pressure and vapor because combustion pressure leaks past the rings/cylinder walls.When the breathers are routed to the intake,vacuum from engine is going to pull that excess amount of vapor through the intake.Breathers to atmosphere aren't going to route the vapors through the intake.As engine "breaks in" (rings seat) the crankcase pressure will reduce,as combustion will be reduced from leaking past the rings into the crankcase.How many miles are on your engine?
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