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Old 09-21-2011, 06:59 AM   #1 (permalink)
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Blow-by to intake: good idea or not?

I know this issue has been discussed at length from the perspective of how to cure blow-by oil from Evo heads, but what I want to know from Evo owners is this: Do most of you have your motors equipped with one of the many intake systems, factory and aftermarket, that sends the blow-by oil/oil mist to the front of the carburetor, or do you prefer to run hoses to the ground or a filter, and keep it out of the intake?

Burning the blow-by seems like a clean, good idea but some riders still insist that any oil/oil mist will result in too much carbon buildup on the pistons. HD intakes use this method now and most aftermarket intake systems do, as well. Are they wrong?

So what does everybody think? Never mind cures for blow-by. Just tell me if you think sending it to the intake is a good idea or not.
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Old 09-21-2011, 08:36 AM   #2 (permalink)
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I never liked the idea of it myself.
My dellkron cases are pre 92 design so it is really not an issue for me. I just plugged off my heads.
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Old 09-21-2011, 06:25 PM   #3 (permalink)
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Sending the breather mist back to the intake is ok in theory, but the problem is that there seems to be no way to get the engine to ingest all of it, so some will go into the engine, and some will slobber all over the engine.

I have a case breather Evo, and I routed the breather hose down the right side of the frame, no filter on the end of the hose (they just get filthy and serve no purpose).
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Old 09-22-2011, 06:16 AM   #4 (permalink)
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Quote:
Originally Posted by Dan89FLSTC View Post
I have a case breather Evo, and I routed the breather hose down the right side of the frame, no filter on the end of the hose (they just get filthy and serve no purpose).
Dan, these canisters work real well. I just drain the thing every two or three days or so. I usually get just a few spoons full of oil out of it. It save ALOT of mist on the rear rim and brake rotor.


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Old 09-22-2011, 05:32 PM   #5 (permalink)
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Quote:
Originally Posted by grndpndr View Post
Dan, these canisters work real well. I just drain the thing every two or three days or so. I usually get just a few spoons full of oil out of it. It save ALOT of mist on the rear rim and brake rotor.
I keep my oil level about an inch below the bottom of the filler neck on my oil tank (`89 Softail), and I never see any oil on the back of the frame or wheel, not even a spot of oil underneath the open end of the hose when the bike is parked.
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Old 09-23-2011, 10:41 PM   #6 (permalink)
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I've always thought of pluming it into the exhaust like they do on race cars. It would be dual purpose if done right it would burn any oil mist and pull a slight vaccum in the crankcase. Although I could be crazy on this one as I've never seen it done on a harley just some food for thought.
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Old 10-12-2011, 03:04 PM   #7 (permalink)
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I used to run a hose under the frame but it would get kinda messy. Lately, since I converted to carb and picked up a Arlen Ness BS, most of it runs into the engine, some of it drips out the filter, but I stuff a small wad of paper tower in the bottom of the air cleaner cover that soaks up any access oil and funny thing, it evaporates and I don't have to change the wad that much.
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Old 03-11-2012, 10:31 PM   #8 (permalink)
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sorry for laughing

sorry for laughing because i have been doing the paper towel wad in the bottom of the air cleaner for a while now and it definitely helps keep my bike clean of oil. i like to think of myself as a little bit better wrench than that but its cheap,easy,and it works fine
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Old 03-14-2012, 05:48 AM   #9 (permalink)
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Got the same issue as many/most of you. I was thinking about the canister
that grndpndr is using ( like the way you got that mounted)
But came across this Krank case vent. Called the guy, and think I'm gonna try it.
Any thoughts/ opinions.

http://www.et-performance.com/kv/kit-3_lg.jpg

going to use the inline, simple.

Last edited by FXRS84; 03-14-2012 at 05:51 AM. Reason: add website link
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Old 03-14-2012, 06:17 AM   #10 (permalink)
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Don't know if it's good or not, but my bikes ingest whatever is left of the blow that doesn't leak out of the bottom of the air cleaner back thru the carbs.
Dan's right, some of it slobbers all over the engine. More on the evo than the TC, but the evo has more miles.
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Old 11-05-2012, 09:42 AM   #11 (permalink)
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Can the crankscase vent line be connected to the oil tank vent line?
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Old 11-05-2012, 03:08 PM   #12 (permalink)
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Quote:
Originally Posted by Chopa View Post
Can the crankscase vent line be connected to the oil tank vent line?
I did that years ago on 650 Triumph and It pressurized the engine! Every seal was leaking oil. It was fine after I unhooked it.
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Old 11-05-2012, 07:48 PM   #13 (permalink)
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I found routing it back into the intake builds carbon on the
intake valve stems.
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Old 11-06-2012, 12:53 AM   #14 (permalink)
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FXR2- I don't know if the blowby is good or bad for the engine, I just don't like the mess. I have tried the paper towel in the air cleaner- it works but a tampon works better. I used a Maxi-pad (with wings, of course) for a while, it had built in tape to hold it in place. Eventually though, whatever was in the air cleaner would blow out. No telling what the driver of the car behind me thought when a oil-soaked pad hit his windshield... Anyway, here is my solution:
í97 Softail, typical EVO head breather venting into the back of a Mik HSR42 air breather. Figured I would try setting up a catch can. I had most of this stuff, but still took a trip to Home Despair to collect all the parts. As you can see it about $10 worth of PVC and brass fittings, and a few feet of tubing:

The brass Tee-fitting in the first picture ties the dual breathers together, then feeds the assembly in the next picture. Ignore the brass elbow, it snuck into the picture and isnít necessary. There are 2 threaded oil nipples used, I drilled a hole for each in the PVC, tapped the holes with a pipe tap and screwed the fittings in. Added a vent hose to the top oil nipple, assembled it with PVC cement, and hit it with a black rattle can.

Starting from the right- the breather vent from the heads feeds into the pipe nipple. The nipple at the top with the short piece of tubing attached vents the gas and vapor. The unit itself is a reservoir that catches and collects oil. At the far left, there is a threaded PVC plug to drain it when necessary. If it sumps enough to fill the reservoir, it will blow out the top.
Here is a shot of it installed and zip-tied to the frame:

I angled it slightly down so the oil would collect at the drain plug. It is not completely out of sight, after I use it for a while and see how much oil it collects I may make a smaller one and try to hide it better.
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