One way Valve on Crankcase Breather?

[Narkotik666]

Howdy,

I've had some problems with the crankcase breather sucking in water. (confirmed by numerous tests...) But that is beside the point.
I would like to know how the system works, because i bought a ONE WAY VALVED Crankcase Breather Hose...very cool...it can "blow out" but not "Suck in"....in theory (it can spit oil and "Blow by's" but it can't suck in water or dust. (sounds great)). but if it IS a BREATHER hose, shouldn't it "breath".....wouldn't this damage the bike somehow....how neccesary is it for the crankcase to BREATH?

this is the last question before i just route the breather to the airbox....just wanted to know if i can stick with the ONE WAY valved breather hose?
Haven't tried it...and i am to worried to try it before i get some facts. don't wanna blow my rings.

Oh yeah, it's a 2005 KX250 that i am turning into an enduro bike. so, alot of rivers and puddles.

thanks.

[bigbellybob]

case needs to vent out only so your good on that. the same for the carb vents they only need to vent out they have one way valves for them too.

[bigbellybob]

you need to have 2 going up high with out the valve.

take a look
http://www.kevinscycleracing.com/intakeandcarburetor.htm

[Motorrad]

I run mine up under the tank, then down again, 

Teory being, if water does get in the line. It has to go up before it can go down in the motor...

I also throw a inline fuel filter on under the tank to keep out the crud

[bigbellybob]

Just like pulling liquid out of a cup with a straw by placing your finger over the top of the straw. Plug the 2 going up and nothing can come out.

I also throw a inline fuel filter on under the tank to keep out the crud

Im going to put one on all my gas cap vents to keep crud from getting pulled into the tank.

[jonny500]

i have never herd of this or the need for it. if you put a 1 way valve on your tranmission breather. as your engine warms up air in the gearbox will expand, this will force air out of your gear box. then when you stop the engine to rest the air will cool, due to the 1 way valve this will cause your gear box to have a negative pressure. i dont know how stong this will be or the effects. but i would say it will have a bad effect on seals. possibly crack somthing if the internal pressure is low enough. like i said i have never done this so i dont know for sure but after having a think for a while this is my conclusion. somthing you think about anyway. any thoughts?
regards
john

[Narkotik666]

i agree.....i thought about it..and surely the pressure in the crankcase should "blow" and "suck" (i should write my own vows).
so i removed the one way valve...and routed it over and back above the chain...so, a chainluber at high speeds....

The Crankcase SUCKS in when you start it. and blows at highspeed......confirmed...
that's why you get water in the crankcase if you stall in a river and kick it there. with dangling pipe.

thanks for the replies

[jonny500]

thats a good point bdi. the intial post says kx250 so i took it to be 2t. as far i am aware a 2 stroke transmision would have no pressure change (only due to heat) as the engine is kept seperate for the transmission. i would say you need to take a look at your crank seals if you are having large pressure difference in the transmision in comparision to atmospheric pressure. i often take my bike through very deep water maybe 3 - 4 ft an have no problems. the japanise bikes are very good providing all seal and rubbers ect are in place. i live in the U.K and weather we have here is wet wet wet most of the time. what say you bdi
regards
john

[bigbellybob]

why do you all believe forks build pressure?

[Narkotik666]

sorry....yup it's a smoker.

would've called it a kxf250 if it was a 4stroke.

[jonny500]

dose the tranmisson oil smell of petrol

[Narkotik666]

no, doesn't smoke (more than a normal 2t (is a smoker afterall)....
and nope....tranny oil is fine......

i get a wee bit of smoke and oil from the crankcase pipe/hose/vent/whatever(the thick black pipe on the side of the crank)....but nothing to be alarmed about (or so i thought).
i am worried NOW though!!!

but she sounds great, feels great, spits like a kx, snarls like a kx and drips like a kx??? (or am i mad!)

ITS A 2005 KX250 2T.

[jonny500]

with a name like narkotik666, then yes you probably are mad lol, now back to your problem, no need to worry we will sort this out. i think the best thing is for you to post some pics of this breather/vent you speak of and anything else you have a problem with as i think we have a terminolgy problem here. dont worry, theres some very good brains on here someone will get to the bottom of it if i cant
best regards
john

[Narkotik666]

YES, i will post pics....since i don't really know WHAT to call the thick black pipe....on the side of the motor "thingy"....

I'll post some. but first i'm gonna get her DOOOOOORTY this weekend. yeee haaa!

i'll post some pics next week.

[Friar-Tuck]

 Sorry to have jumped in so late,
Here are some examples that will help solve your dilema I think,  http://www.daprorubber.com/duckbill-flapper-umbrella-valves.aspx
  A duck bill valve placed near the end of your crankcase breather will let pressure in and out, and still give you some protection against ingesting water.  It's designed to be one way, but realistically
it's not going to hold a vacuum too long.

Here are some solutions the Harley Guys have come up with, they have been battling this for a long time...http://www.cas4.com/engine/engine-crankcase-breathers-breather-valves2.html

How fast can you afford to go?

  Tuck\o/