breather pipe



37 replies to this topic
  • YZ_MAN

Posted March 08, 2001 - 07:43 PM

#21

I put a k&n filter on the and of the vent hose of my 2001 YZ250F and put it in my air box. I think a pcv valv would not be a good idea I would not want the oil pump to incounter any abnormal presure and hinder oil flow. I twist tied the filter to the side of my air box.

  • YZ_MAN

Posted March 08, 2001 - 07:48 PM

#22

What dose KTM sx 400 and 520 go about useing a vent hose I have never seen one.

  • techman

Posted March 09, 2001 - 04:58 PM

#23

I'm still waiting for a guru-expert-god guy like Eric Gorr to answer my question, "just how much blow-by air comes out the breather?"

Puuuulllllleeeeeazzzze answer! Let's settle the issue with a QUANTITATIVE result, not guesses at the importance of principles and effects. The reasoning presented so far is generally valid, but the size of the effects is never stated.

Is it like less than 1% of the volumetric throughput of the engine? I would hope so, or rebuild the engine!!!!! Maybe its less than 0.1% of the volumetric throughput of the engine!!!!! Please correct me if these figures are wrong!!!!! Or else, this large debate is about sucking in <1% poorer air quality re oxygen content!!!! A warm day probably has more effect on losing horsepower!

I completely stand to be corrected when the QUANTITATIVE % of volume blowby figure is finally presented.

Com'on engine gurus! Gimme some numbers!

  • YZ_MAN

Posted March 09, 2001 - 10:05 PM

#24

Yes a true anser would be nice I think yamaha needs to take aection on a new set up. I've heard of the YZF and WR sucking up dirt because of this vent. That is why I put a K&n cranck case vent filter on the end and put it in my air box. UNI makes a good cranck case vent fliter to. I have had no probleme with this setup and I suggest the same setup to anyone who has a YZ or WR :) . I don't think a pcv valv is a good idea I would not wont the oil pump to incounter any abnormal presure and hinder oil flow. I think my setup is the sefest.

  • techman

Posted March 21, 2001 - 10:20 PM

#25

For someone with a few minutes and their breather tube still out the bottom of the bike, maybe try this experiment.

Use a twist tie to seal a plastic bag like a grocery bag, kitchen catcher etc onto the end of the breather tube. (Make sure to keep it away from the exhaust!!!) Fire up the bike, rev it up to mid rpms, big rpms etc and keep track of how long the engine runs. Then see if/when the bags gets filled up. We can estimate how many revolutions of the engine occurred and estimate the volume of the bag.

I know someone adept will say the quantity of blowby is engine load dependent, so phase two of the experiment could involve load other than the inertial load of building engine rpms. Either way, if it takes minutes to fill the bag then the blowby is next to nothing. E.g. 5,000 rpm x 400cc/(2 rev) = 1,000,000 cc in a minute through the engine (if at full throttle) Grocery bag = 6 liters = 6,000 cc. That would be 6,000 / 1,000,000 = 0.6% blowby.

  • Tom_N

Posted March 21, 2001 - 12:37 PM

#26

WOW - this is getting scarry.. I mean all the math and talk about gasses, percentages and the like.. :)

In the several minutes I have spent reading, I first was going to re-route my hose (I know but don't say it) then I was not, then I was, then I was not, then I was again and so one...

I think I will just make sure I don't stall it in a big puddle of water and if I do I will walk it out and make sure the tube is clear before I kick it over...

Ride it more work on it less and have fun!

  • motoman393

Posted March 21, 2001 - 01:06 PM

#27

hey Tom...I dont know about you or anyone else but I almost have as much fun working on my bike as a do riding it (except for changing/flipping front and rear tires, that is a pain)!

Garrett

------------------
I get my kicks on a 2001' YZ426!
Friendswood, TX

  • techman

Posted March 22, 2001 - 03:14 PM

#28

It's like watching ping pong from the side!

Frankly, you're safe rerouting it any old way you want, in fact don't even reroute it and just stick a filter on the end (except that it would get ripped of under the bike). A little water won't kill you near as bad as grit in the engine would. Just keep the grit out 99% of time and do your best to keep water out.

I may even get ambitious and do the experiment myself. But then again I've been hp addicted with my bike's awesome performance for all of last year, all while sucking in the dreaded blowby! When it won't just stand up in third anymore I'll start to think I might be down on power.

  • oldnbold

Posted March 23, 2001 - 11:08 AM

#29

Well, I'll probably get crusified for this but here it goes... On Doug Henry's 1st yzf there was an article about it in MXA. It had many trick go fast parts on it, and many didn't make it into production. One of the go fast parts was a brazed tube into the exhaust headpipe that lead to a diaphram of some kind that then lead to where our current blowby hose is attached to the valve cover. I could be delusional about the diaphragm, but what I gathered from the explanation of that part was this was similar to race car technology utilizing the exhaust gas mass /flow to create a vacuum within the crankcase. As DaveJ stated, motors work easier in a vacuum.

Anybody want to try this and give a report?

I can't braze anything, and can barely handle the stock hp.

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

Posted March 23, 2001 - 11:48 AM

#30

Is there any reason why you couldn't just cut the hose shorter?? Does this hose have anything to do with the performance of the bike? or is it truly just a breather hose?

  • DaveJ

Posted March 23, 2001 - 02:53 PM

#31

Amador,

Technically it does not have to be any particular length. But along with the gases comes the occasional oil drip, which would not do much for your leg and boot.

This can also be a concern if you loop it up into the airbox since the fluid would get trapped at the bottom of the loop.

I still say run a T breather - this let's the fluid and most of the gas go out the bottom, but prevents a vacuum from forming when in water.

DaveJ

  • PMK

Posted March 23, 2001 - 04:26 PM

#32

If you get the Yamaha promo poster of Tim Ferry you can get a decent look at the system. I got the poster and took a look at the bike at Daytona.

This system is similar to the system on several of the aicraft I maintain.

This is what I think Yamaha has for a works breather. Because the engine is wet sump it needs the oil seperated from breather air and the little can is an air/oil seperator. The seperator also has a valve or diaphragm inside to prevent exhaust pressure pulses from entering the engine and causing pressure, leaks or popped seals.

Overall this is how I beleive the entire system operates. The exhaust header has a tube weld into it at an angle so as to create negative pressure when exhaust flows down the header. This is connected to the air/oil seperator (which allows breather air to flow out the exhaust and oil to drain back into the cases). The oil seperator inlet connects to the valve cover similar to the stock 426 breather except on the side of the valve cover. Then the original breather hose connection at the top of the valve cover allows filtered fresh air to enter the system and also serves as a normal breather when positive pressure may exist at the air/oil seperator.

Then again maybe it's nitrous.

PK

  • PMK

Posted March 23, 2001 - 04:28 PM

#33

If you get the Yamaha promo poster of Tim Ferry you can get a decent look at the system. I got the poster and took a look at the bike at Daytona.

This system is similar to the system on several of the aicraft I maintain.

This is what I think Yamaha has for a works breather. Because the engine is wet sump it needs the oil seperated from breather air and the little can is an air/oil seperator. The seperator also has a valve or diaphragm inside to prevent exhaust pressure pulses from entering the engine and causing pressure, leaks or popped seals.

Overall this is how I beleive the entire system operates. The exhaust header has a tube weld into it at an angle so as to create negative pressure when exhaust flows down the header. This is connected to the air/oil seperator (which allows breather air to flow out the exhaust and oil to drain back into the cases). The oil seperator inlet connects to the valve cover similar to the stock 426 breather except on the side of the valve cover. Then the original breather hose connection at the top of the valve cover allows filtered fresh air to enter the system and also serves as a normal breather when positive pressure may exist at the air/oil seperator.

Then again maybe it's nitrous.

PK

  • techman

Posted March 26, 2001 - 12:24 PM

#34

Hi Guys, noted your comment about "looping" the hose to the airbox. Actually, on my setup it runs almost always level or upwards to the top of the frame. I've never had oil make it to the end of the hose yet. I think it just runs back into the head and has no place to pool at. PMK, I read in the literature that the engine is dry sump, not wet sump. (?)

DaveJ, here's a thought - with your engine running, in the stock setup the gases supposedly always coming out prevent the water from rising up the breather (like soda filling the submerged part of a straw). When you open the top with a T, the water now rises happily up, and if you go deep enough to get the top of your cylinder head in the water, the water will just run right into the engine. To prevent that you'd have to put the T higher than the deepest water you expect to hit, kind of like a snorkel. A more robust version of the solution would be a PCV valve that only lets gas out at the bottom hose, and another that only allows gas in at the top hose.

  • DaveJ

Posted March 26, 2001 - 02:59 PM

#35

Interesting addition.

So let's see. The only time this whole breather pipe issue is a problem is when you have the tip of the breather pipe in the water at the same time you have a strong enough vacuum at the breather pipe.

Without a vacuum, and without pressure, the breather pipe would only fill up to the same height as the water level. This would occur regardless if you had a "T" in place or not.

If you are really taking a bath, it's possible that the water would rise more easily up the breather pipe with a "T" in place than without. I'll buy that.

For those that really like to go deep, you'd have to loop the breather tube up, then "T" out that second “fresh air” tube, running that somewhere high. Perhaps the back of your front number plate...or the corner of your mouth.

If you're able to keep your engine running in water that is higher than the highest point of the breather pipe loop, you'll then need to purchase a new crank.

  • techman

Posted March 31, 2001 - 07:29 AM

#36

Hi Dave,
Minor point: with the stock pipe, the crank case is a sealed container with only the breather as an opening. Therefore, with a stopped engine (i.e. stalled) you could have water up to the gas cap and it wouldn't be able to flow up the breather (pinch the far end of a straw and try to squirt water up the open end) ... UNTIL you try to kick the engine over while submerged, at which point the piston acts as a big syringe pump on the up stroke and sucks 426 cc of water up the tube.

If you cut a hole near the pinched end of the straw (i.e the T'eed hose up near the cyl head) now you can squirt water up the straw. On the bike, once the water got to the T junction I'm assuming its downhill into the head from there and hence water would just flow into the head.

So therefore, no T and no attempted kick will actually prevent water from rising up the breather. The kick is the fatal act. Or, if T'eed, you've gotta keep the T above the water level (unless you use PCV valves).

Practically, the bike is "snorkelled" already up to the bottom edge of the seat, or top of the airbox. So, once you go in that deep you're doomed anyway because the carb will suck in water. Therefore you only need the hoses up to the top of the air box or roughly the height of the steering stem.

As far as watering out and bending the crank, with some luck the first dribbles will wet the plug or wreck the mixture, stop ignition and the engine will stop before it attempts to pull in a full gulp of water, kind of like when there's water in the bottom of your float bowl and the engine stops as soon as it gets water instead of gas in the atomised mixture.

I'm going to do the PCV valve thing when I get the chance. I just know that one day the slippery rocks are going to get me and I'm going to lay the bike down in a creek.

  • DaveJ

Posted April 02, 2001 - 10:08 AM

#37

Techman,

Sorry - been out for a bit.

Anyways, it doesn't sound like were are really saying anything too different. I understand each of your points and you obviously know what you're talking about.

So , perhaps I didn't make my posts clear enough.

Is there anything you can think of that I'm completely missing that may be a concern for others dealing with this?

DaveJ

  • techman

Posted April 02, 2001 - 03:58 PM

#38

DaveJ, I think with us working out all these details it has ended up as a good educational documenting exercise for the masses.

I'd say that's pretty much the purpose of forums. It feels good to contribute :) and talk shop with fellow riders.

Ride on!





Related Content

Forums
Photo
Motocross

Thinking about Yamaha 250... by Arctic Pride


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies
Forums
Photo

First Hare scramble tips by dhend8


Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  33 replies
Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
Forums
Photo

James Stewart back on a YZ450F by YamaLink


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies
 
x

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.