[jvdixon]

I have a 98 evo head breather motor. To get rid of drippy air filter, I lengthened the outlet hose and ran under frame to the atmosphere.
I was wondering, since originally the hose vented inside air filtered area to carb, it was adding some air to the air/fuel mixture slightly? If you put your hand over the hose when engine is running, you do feel air pushing (and of course oil mist).
I wonder if it affects maybe the air/fuel mixture at idle or so?
I have noticed a little difference on cool damp morning lately.
It's a mikuni hsr42 out of the box for an evo (stage one style headwork and a ev27 cam)
I'm no official mechanic, I'm interested in others opinions
Thanks

 

[Alan S]

The crankcase vent is irrelevant to the air/fuel mixture.

 

[Stovebolt 55]

The engine will pull in what air it needs through the path of least resistance I would not worry about the insignificant amount coming through the breathers as affecting the a/f it’s the oily mist that is affecting it more, that you don’t want going in there.

 

[<G Man>]

I have a 98 evo head breather motor. To get rid of drippy air filter, I lengthened the outlet hose and ran under frame to the atmosphere.
I was wondering, since originally the hose vented inside air filtered area to carb, it was adding some air to the air/fuel mixture slightly? If you put your hand over the hose when engine is running, you do feel air pushing (and of course oil mist).
I wonder if it affects maybe the air/fuel mixture at idle or so?
I have noticed a little difference on cool damp morning lately.
It's a mikuni hsr42 out of the box for an evo (stage one style headwork and a ev27 cam)
I'm no official mechanic, I'm interested in others opinions
Thanks

The static pressure in that tiny hose is way less than the suction from the cylinders. It makes no difference at all in AFR. The only difference would be from lack of oil mist.

 

[Brand'd]

I would suggest if you're getting significant oil "mist", as you call it, coming from your hose you may want to look at replacing the umbrella valves in the rocker boxes. They dry out with age. A good running motor doesn't blow much oil at all.

 

[jvdixon]

Ok, that's a good explanation. What do you think of the S&S reed breather

 

[jvdixon]

This engine has 5k on new James gaskets umbrella valves. When I was fixing a couple broken bolts in cone cover, I threw I the reed breather. The nylon timing breather looked ok, I was just updating stuff preventative. Bottom end had 120k miles. All next top end was done.
Reed seems to blow more oil, but I do tend to ride it harder now

 

[Pebhvac]

If you lengthen the breather line a bit and make a trap in it you'll minimize the oil spray.

 

[Brand'd]

If you lengthen the breather line a bit and make a trap in it you'll minimize the oil spray.

This is a common "bandaid" fix. You're not fixing the problem, you're just covering it up. It's like thinking you've solved the problem of oil dripping onto your driveway by placing a pan under your leaky vehicle. Sure, you've stopped it from making a mess, but it still leaks.

 

[Pebhvac]

At 5k miles she's still fresh. It should level out on her own

 

[<G Man>]

This is a common "bandaid" fix. You're not fixing the problem, you're just covering it up. It's like thinking you've solved the problem of oil dripping onto your driveway by placing a pan under your leaky vehicle. Sure, you've stopped it from making a mess, but it still leaks.

Well, technically, the pan under the vehicle would solve the problem of oil dripping on the driveway. Jus sayin

 

[Brand'd]

Well, technically, the pan under the vehicle would solve the problem of oil dripping on the driveway. Jus sayin

Yeppir and that's what I'm saying. They see the result of the issue. Not the issue.