Crankcase Breather Pipe

73 replies to this topic
  • SoCalWR426

Posted January 21, 2002 - 05:26 PM


Excelent postings, I too blocked off all vent to airbox then to atmosphere. when racing ZX10's Simple way to put it is..
Running vent to airbox makes your bike eat it's own poop! Just like epa likes it..Yech! :)


  • Ronin

Posted January 21, 2002 - 05:40 PM


Thanks SoCal, I love the analogy. It just pains me to see the posts about putting the breather into the airbox, us Buellers take so much time, effort, and cash to properly remove that crap from our bikes it almost strikes me as blasphemy to think about putting a crankcase breather into an airbox of a bike that already has its breather vented to atmosphere.



  • John_H

Posted January 21, 2002 - 05:45 PM


Hey Ronin,

I too have seen an obnoxious amount of crud in my Harley and Buell's airboxes. Hell, I don't even oil my K&N on the Harley because the crank case does such a good job.

Seeing all the crud that comes out of my WR's vent tube makes me think it's probably as bad. I really don't like the idea of sucking all that stuff back into the box. It makes sense that the EPA doesn't want it going on the ground either.

I'm wondering if the tube might even get clogged up with the crud if there is a dip in the tube???

  • Ronin

Posted January 21, 2002 - 05:50 PM


John, you may be right on the clogging of the tube, but maybe all the moisture keeps the crud from building up too bad. I too have friends who dont oil their K&N filters due to the oil spewage. However, I have them all on Hayden crank vents with a little K&N filter on the end of the breather hose. This setup keeps everyone happy. H-D makes a bridge for both the cylinders and then the bridge routes towards the back of the bike where you can put a vent and filter. We sell a ton of these at the dealership where I work. you might want to look into this for your H-Ds and Buells.


  • Nige_Uk

Posted January 22, 2002 - 02:18 AM


You boys do things the hard way (& expensive !!), my way of solving this problem was to cut into the main breather pipe just below the bend, epoxy in a 'T' piece (from your local DIY store) in, connect a new piece of hose (same size as original) to the 'T' & run it below the fuel tank & up ontop of the air box. Place an air filter on the end for good measure (pneumatic fittings - nice & small).
If the bike stalls in water where the original breather is in the water, air will be drawn from the pipe located under the seat/ ontop of air box.

If the bike is totally immersed in water (engine stopped !!), & water gets into the pipe under the seat, when the bike is stood up, water will run to the ground via the 'T' into original breather pipe. Alot of people route the original pipe up to the bars, but if water/condensation gets into the pipe, it will end up in the head !!

I've done this mod on both my WR's & works fine



  • Guy

Posted January 22, 2002 - 08:23 AM


Originally posted by Ronin:
Thanks SoCal, I love the analogy. It just pains me to see the posts about putting the breather into the airbox, us Buellers take so much time, effort, and cash to properly remove that crap from our bikes it almost strikes me as blasphemy to think about putting a crankcase breather into an airbox of a bike that already has its breather vented to atmosphere.



But there is the point my good aint a Buell, just cos your thoery applies to one particular make it doesnt ness apply to all does it?? With the greatest of respect to all you Buell /Harley riders, Other than two wheels they don't have a lot in common with the rest of the motorcycling world now do they? (more Massy Ferguson LOL)
The best way is to disagree and when I've modded MY WR I'll report on whether it's right or wrong good or bad, one thing for sure , it aint blasphemy just cos you dont like the idea now is it? :)

  • Ronin

Posted January 22, 2002 - 09:43 AM


Whatever, its your with it however you want.


  • Guy

Posted January 22, 2002 - 01:26 PM


:) Ooops, Sounds like I trod on someones toes! Oh well never mind :D

  • imported_Scott_H

Posted January 22, 2002 - 06:04 PM


Interesting thread.

I’ve been running the ‘Clark Mason breather routing’ (up behind the number plate with a small K&N filter attached to the end) for close to a year and half now with no problems including no filth/gunk build up. I have cleaned the small gauze filter about four times since installing it. It just doesn’t get very dirty up there. See http://www.thumperta...ic&f=3&t=003246 for additional info.

I found out the hard way water ingestion can be a problem even in the middle of the Mojave Desert. I managed to pretty much submerge my bike about 40 miles outside of Barstow last November on day two of the LA-Barstow to Vegas ride. The course took us through two ~50 foot long ~3 foot deep water crossings. I cruised through the first one without any problem, but on the second one, I ended up rolling into what was probably the only hole in the river bed resulting in the water rising to just below the gas cap. I pretty much floated off the seat! I let off the gas as soon as the front fender started to submerge and the bike instantly stalled. Before I did anything with the kick start lever, I pushed the bike to dry ground, pulled the seat and tank, drained the air box and carb float bowl, wrung the water out the air filter and pulled the sparkplug. I was able to see no appreciable moisture in clear 1/2 inch PVC braided hose I’m using for the crankcase breather, so I didn’t mess with it. I then kicked it over a bunch with the plug out (tank still removed) until there was no real signs of moisture being blown out of the sparkplug hole. I then checked the plug for spark before putting everything back together, which was a good thing since it turned out I had no fire. After reseating most of the connectors in the wiring harness, I finally got a spark. Put it all back together and it started in 4-5 kicks. It took me a little less than an hour and half to get it going (I would have houred out had this been an enduro!). I rode the remaining ~200 miles to Vegas without any bike problems (I won’t discuss the self inflicted rider induced problems here). One lesson learned from this is, I have gone back and applied a healthy dose of dielectric grease to all my electrical connections for improved waterproofing.

Getting back to the breather routing that terminates behind the number plate – I have never noticed any significant condensation that could potentially accumulate and run back down into the valve cover. As you would expect, I am able to see a small amount of oil residue the collects in the hose. My guess is the condensation issue is probably a bigger concern in higher humidity climates. I’ll try to pay closer attention to it the next time we get a reasonable amount of moisture in the air out here.

I really like SoCal426’s analogy and especially the “just like the epa likes it” comment – that’s great!


  • SoCalWR426

Posted January 22, 2002 - 06:47 PM


scott h,
You didn't need a breather, you needed a snorkel :)

Well...As you know, You can lead a horse to water.......

Guy in U.K,
Your a different matter here. To tell a guy his experiances both past and present are not worth considering because it's not with what YOUR ride might be at the moment. You didn't step on his toes. You God^*%# insulted the man while hideing behind the (just an opinion) excuse!! Ronnin put in great detail, time and thought in his postings. I've never meet the man and he proved himself a class act to me by his response to your ravings.. Well he let you off light!. Your response in return just showed to us all that YOU have NO Class..Oh yea!..Just an opinion.


Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Guy

Posted January 22, 2002 - 09:23 PM


:) SoCal, I'm afraid you've mis-understood me if you think that I think that Ronon's comments, are invalid and Rubbish, my point is that not all motorcycles are tha same, I totally accept that for Harley's/Buells etc all the issues he has brought up, The way he talks , he obviously has Great understanding of HIS issues with this, BUT I want to experiment for myself, which ws the point I am trying to make, MY thoughts run down a different line to his thats all, MY experiances with other bikes are different to his, and yours, This is a DISCUSSION board, different view points aired, NOT a THIS IS THE WAY TO DO IT board, It's not a question of class, it's more a question of being Adult enough to accept that there are different views to your own and "more than one way to skin a cat" Already on this thread alone, there have been at least three or four DIFFERENT methods of the crank breather....and everyone is happy with their solution!
I had come to expect an exchange of valid points, NOT a "WELL your wrong cos I say so" and "You've no class because you disagree" from this board
to say I'm a little disapointed is an understatement, name calling does no-one anygood at all I would suggest that You, SoCal re-read all my posts on this subject, and try to see exactly what I am trying to say.
IF all I get is another "NO class" or "Whatever!"
I rest my case!

[ January 24, 2002: Message edited by: Guy ]

  • Guy

Posted January 22, 2002 - 10:07 PM


AND just as a further point SoCal, I would really like you to point out the part where I
1) Insulted Ronin,
2) Told him his points were invalid and worthless
3) hiding behind an excuse?!?!?!?
4) Just exactly where was I "Raving"?
IF you read it properly, many times I state," Yes I understand where you are coming from"
AS I said OPINIONS, not direction from on high,
My feelings are that it is NOT myself showing the "Lack of Class"
Dont Diss me, just because I dont follow the flock!
If we take this to the Nth degree, ANY bike which has such a serious oil mist/airbox fouling problem, that most owners don't even oil the filter, Should we really consider it to be....
"The One which ALL others follow"
I dont think dont diss me for having the balls to say, "yeah fine, but I'm doing it my way."

[ January 23, 2002: Message edited by: Guy ]

  • Guy

Posted January 23, 2002 - 09:52 PM


:) SO I see, SoCalWR426, you'll throw the mud, but ya can't take it can Ya!? :D

[ January 24, 2002: Message edited by: Guy ]

  • Guy

Posted January 23, 2002 - 09:53 PM


[ January 23, 2002: Message edited by: Guy ]

  • Ronin

Posted January 24, 2002 - 03:59 AM


Guy, I have been thinking of all the mods you have done to your bike and wondering....Hmmmm....I havent seen anything about a lowering kit or shaved seat or anything like that. So I guess my question can a 5 year old touch on a stock height Yamaha. I mean hell, I am 5'9" tall and I can barely touch one foot with boots on. And that is only after I lowered the forks in the triple trees. You must have some kind of genetic mutation. Or maybe...well thats just a whole different thread.


P.S. Maybe you should back-off a bit here.

  • SoCalWR426

Posted January 24, 2002 - 07:16 AM


I Rest my case...


  • AK-thumper

Posted January 24, 2002 - 09:49 AM


The Buell input is great because it does represent a worst case solution. The Buell engine has two pistons moving about the same amount of air each as a WR at about the same time (narrow v-twins move both pistons up and down at about the same time), with a smaller crankcase volume. The WR has a common transmission/crankcase where the buell does not making the Buell move more air in less volume=more pressure differences.

Of all the solutions presented a single tightly sealing PVC-type valve to atmosphere (or the airbox) is the only one that will keep water out of the crankcase when you drop your bike in water.

Not really a subject worth arguing about guys.

  • Ronin

Posted January 24, 2002 - 09:57 AM


AK-Thumper, you are right on in every point. especially the last one.


  • SFO

Posted January 24, 2002 - 10:14 PM


I hate to interrupt this love in but I am interested if anyone actually has experience running a pcv valve on their yz.
If so what one are you running?
Perhaps I would pull the bung out of the valve cover and pipe tap a home for it.
Sorry for butting in, y'all may continue now...

  • Ronin

Posted January 24, 2002 - 11:40 AM


SFO, I havent actually ridden my WR with a PCV valve installed. However, on my Buells I run Hayden crank vents. I did try the Hayden on my WR and stuck the breather tube in a bucket of water. Then I held down the kill button and kicked it over for about 10 minutes to see if it would suck up any water. It did not, the bike did seem to run fine with the PCV valve installed. I have heard only good things about the Spyke Krank vent too. Just make sure it is a motorcycle PCV valve so that it dosent stick in any position if you were to tip over or do a big wheelie or something.



Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.