Crankcase Breather Pipe

73 replies to this topic
  • John_H

Posted January 28, 2002 - 06:37 PM



My '01 wr leaves a bit of oil from the tube everywhre I park it. I'm suprised that it doesn't require any oil added between changes. Usually every 150-300 miles.

  • SoCalWR426

Posted January 30, 2002 - 02:20 PM


Oh, By the way......I run mine stock :) :D

  • Guy

Posted January 30, 2002 - 10:54 PM


Originally posted by SoCalWR426:
Oh, By the way......I run mine stock :) :D

:D Is that toatally stock ? or have you fitted a filter to prevent any possibility of dirt ingress? :D

  • SoCalWR426

Posted January 31, 2002 - 05:31 AM


Hi Guy,
At this point it's totaly stock. 02 WR runs tube down front of frame & ends at skid plate left hand side.( I don't know about earlier models) I don't get any oil or residue/debris at all on my bike at this point. I do plan on removing breather tube from time to time and clean it out and see if any dirt comes out. If it appears dirt is traveling up the tube then I will consider an inline filter. But I am concerned that a filter can trap water or moisture. Thats where a pcv comes in. Do I want to go there? No. I don't want to even think I can build a better mouse trap. I'm a firm believer in the KISS principle. I don't believe that we can pull enough inches of vacuum to pull water up into our motors, If that was a real concern I'm sure the wee people and their slide rules would have come up with our plan or versions of it. (our plan = all idea's presented here) I think that all the hydro problems (I'm sure there's exceptions) are from water entering through intake vs breather.(e.g) I stalled my bike in kinda deep water and could not kick it over. whats kinda deep? Up to your seat? Over it? Were you going balls-out and hit a 3-4ft crossing
and you were a human wave machine? Did you fall while making the crossing? Motor's just don't do well injesting huge amount's of water. I've made water crossings up to my seat and been fine, I've hit 1ft crossings at mach 3 and been fine, but, I've been screwed too! Bike goes upside down with sparky out and pumping away. I've also seen and helped guy's pump gallons of river water out after falling in crossing and bike tries to be a submarine. I'm more concerned to an obvious point, in how I cross for the conditions.... Just my 02's worth..Did I answer the big breather question presented here? I don't think so.. It's up to each one of us to look at the info available here and go with what in their own mind works best...Me, personaly I'm saving those brain cells for how to clear those double jumps and deep whoops that kick my ass and scare me :)

Michael Armstrong

  • Guy

Posted January 31, 2002 - 08:44 AM


:D SoCal....what can I say....what an in-depth and totally honest answer to a simple question...I know where you are coming from..."If it 'aint broke..don't fix it!" :D to some extent, I couldn't agree more, I think "Our" discussions, point of view. etc have certainly helped some people think about what they want, Ronin, for example, in spite of his obvious expertise in "Buell-dom" realised that there are other way's, MXTuner, runs his bike to the boot with NO problems :D and NigeUK with the most simple and effective answer(which I would use if I hadn't already "butchered" my hose :D )
a Good discussion which has brought forth some fine ideas, well worth the temporary mis-understanding :D
The 9only way to find out if the engine could lift water would be to affix a vac gauge to the hose and kick it with the kill button held, I think Ronin did something similar and did report water at the PCV...but I don't know where he placed the valve :D
The thing which sparked all this off for me, was a report in one of our Enduro magazine's which stated that someone had Hydro-locked a motor by kicking it in deep water,but as you say, how deep is DEEP?
A bit like you the only drowned bike I've had the mis-fortune to have to sort out was a totaly submerged one!, as you say, no PCV/filter, whatever is gonna keep that out :D
My only reply to your comment on the "little fella's with the slide rule" is..........."JETTING/ APJ" ..if you get my drift he he he he! :)
keep it up!

  • Rich_in_Orlando

Posted January 31, 2002 - 09:38 AM


One interesting side benefit I realized from replacing my breather tube with a clear hose was that I could see exactly how far dirt was traveling towards the motor. I wanted to put a filter on it (as I stated above) because when I routed it up behind the steering head, I shortened the tube and didn't want to suck in dirt. But, I could see that dirt didn't make it very far up the hose before it was captured by the coating of oil in the tube. The last inch or so was pretty dirty, and you could see the discoloration from the oil getting dirty, but gradually cleaner the closer to the motor it got, in the last six or so inches of the tube but after that it was pretty darn clean. I figured that if dirt was getting all the way up the tube, you would see it all the way up the hose but that just wasn't the case. I have since returned my breather hose configuration to the stock position and have kept the clear tube (because I had a surplus of it and didn't want to buy any more hose if I didn't need to.) But I'm confident that dirt isn't making it to the motor from the breather hose.

  • Ronin

Posted January 31, 2002 - 09:54 AM


This is one of the best threads ever, we all had pre-conceive ideas when coming into this discussion. We talked, argued, and discussed the ins and outs of the breather question, and now at the end we all left with a better general understanding of how our bikes work and what other "experts" (I use that term loosly) feel and understand about it. This is the perfect thread to show why forums are so important to the further advancement of "field" engineering.


by the way: sometimes I think we (the actual users) come up with some of the best real world ideas for our equipment.

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  • SoCalWR426

Posted January 31, 2002 - 11:34 AM


This thread is making me CRAZY!! Just when I think it's gonna die, It resurfaces bigger and stronger than before. I don't know wether to shoot it or feed it :D But it's great as Ronnin said.
Guy, you got me on the jet/apj :D Way overboard and complicated. Good thinking and great example.

Rich, Clear hose was a good indicator on how things really work out.

Ronnin, Your also right re: end user's come up with real world solutions..

Guy, I would also run the vac gauge while running at all rpm's, so as to see inches actually drawn in all

Nige, You-Da Man!!

Gentlemen my helmet's off to you :D

I can't wait for our next topic/saga that has even more opinions, somthing real earth shatering, like. Hmmm....Handle bar bends :)


[ January 31, 2002: Message edited by: SoCalWR426 ]

  • Guy

Posted January 31, 2002 - 02:44 PM


:D SoCal, It's funny you should mention Handle bar ends, I was having a conversation the other day....................... :D :)

  • SoCalWR426

Posted January 31, 2002 - 02:50 PM



SoCal :)

  • ballistic

Posted January 31, 2002 - 06:02 PM


Wheres the consensus? Whatever... I'm gonna tee them together and stick a KN crankvent filter on there as a bonus... good enuff.
I wonder if a small fuel filter would work.... hmmm..

  • JohnL

Posted February 01, 2002 - 03:52 AM


Good or bad, I have just fitted a T - piece and clear tube rising under the seat and ending ontop of the air box. The filter is a bit of sponge with a small hole in it and gaffer taped around the end of the clear tube. And it all (appears) to be working great.

  • Guy

Posted February 01, 2002 - 08:24 AM


Originally posted by ballistic:
Wheres the consensus? Whatever... I'm gonna tee them together and stick a KN crankvent filter on there as a bonus... good enuff.
I wonder if a small fuel filter would work.... hmmm..

:) I think the consensus is that there seems to be NO definitive Right or wrong solution, do it how it seems right to you for your riding and area that you ride in, ie lots of river crossings, think about putting it in the box, lots of dust, filter etc etc......... :D

  • techman

Posted November 15, 2002 - 02:01 PM


Here's my experiment for today. Let's see if/where this thread pops up, being so old and possibly from before the forum format changes.

On the actual thread topic, an option to a bought filter is a block of foam with a small hole in it, zip-tied to the end of the hose. Any oil misting only serves to oil it as in like a normal air filter. The foam also damps the air resonating in the tube length, while letting a net air outflow occur if necessary. The oiled foam serves to slow down water ingress if needed, although not in a sealed fashion like a PCV valve would do. I also posted somewhere a long time ago about running paralelled (sp?) PCV-like valves that would allow flow in either direction but have just enough opening-resistance (i.e a spring preloaded PCV valve, not a gravity-seated PCV valve) to resist a small head of water pressure to prevent water ingress in a submarined bike, assuming you don't kick or e-start it while it's severely submarined. I.e push it out of the water and then start it. I was considering the case where the bike was in so deep you likely flooded the intake tract already too. Almost forgot - this was with the tube tip in the air box just below the seat, outside the air filter in the dirty air, but with a bike dumped on it's side in a creek etc it would be well below the water surface.

Now let's see if this thread rises from the dead... ;-)

BTW great disclaimer!!


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