KX Riders
Maintenance & Technical => KX250 / KX125 => Topic started by: Narkotik666 on June 20, 2010, 11:34:54 PM
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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.
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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.
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you need to have 2 going up high with out the valve.
take a look
http://www.kevinscycleracing.com/intakeandcarburetor.htm (http://www.kevinscycleracing.com/intakeandcarburetor.htm)
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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
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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.
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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
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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
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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
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why do you all believe forks build pressure?
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sorry....yup it's a smoker.
would've called it a kxf250 if it was a 4stroke.
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dose the tranmisson oil smell of petrol
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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.
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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
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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.
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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/
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i totaly agree with bdi's last post. i have alot of experience with 2 stroke mx bikes and by the sound of it so dose bdi
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On my carb breathers I have connected the outlet pipe to a T piece, one part of the T faces down to the bottom of the bike and the other goes up into the airbox.
That way if the bikes in water the breather can't suck water up as the top pipe doesn't allow it to get any vacuum.
I assume it wouldn't be too hard to do the same with the transmission as well if needed.
There's a picture showing the setup that I copied here...
http://books.google.co.uk/books?id=kuYFuUqzNBMC&pg=PA100&lpg=PA100&dq=carb+T+vent&source=bl&ots=wK5lV5DLii&sig=luUXDuL5Md1hNONFxcPULZ-Af3s&hl=en&ei=ugklTOTIDMaSOOK_jLkC&sa=X&oi=book_result&ct=result&resnum=8&ved=0CDQQ6AEwBzgK#v=onepage&q=carb%20T%20vent&f=false (http://books.google.co.uk/books?id=kuYFuUqzNBMC&pg=PA100&lpg=PA100&dq=carb+T+vent&source=bl&ots=wK5lV5DLii&sig=luUXDuL5Md1hNONFxcPULZ-Af3s&hl=en&ei=ugklTOTIDMaSOOK_jLkC&sa=X&oi=book_result&ct=result&resnum=8&ved=0CDQQ6AEwBzgK#v=onepage&q=carb%20T%20vent&f=false)
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uurugh....okay, i better get some images of what i'm talking about.
i think i might be giving the wrong info. (i hope)
or that i am giving the right info (then i'm worried)
Doom prophecy.
but, surely, there will be so "sign" that the motor is going to pop....like sloppy throttle response, low power,etc etc etc.....if the seal are cooked and the motor is going to EXPLODE.
trust me.....the thing is as responsive and snappy and snarley as a squirrel on speed. (at the moment).
but i will post pics of what i'm talking about. and a full description of symptoms. before i loose a motor...cause i am taking the bike too "hell" this weekend......
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okay, attached pictures. (hopefully)
where the new WHITE hose comes from, is that the crankcase breather?
it used to be a thick black hose that pointed down, and some oil and smoke would drip out of it (little bit, after and during some hard riding...it doesn't leak though.....) (is that normal?)
with the hose pointing down setup....i used to get water in my oil, from rivers and obviously trying to kickstart it in rivers with the end of the thick black hose submerged.
The second setup i tried, was with the thick black hose pointing UP....and with that...i had BEAUTIFUL GOLD OIL, after riding rivers and mud and puddles....so, it didn't suck in any water...but i had oil all over my pants and engine....as you can see.
so, what i did, is attach a longer white hose (it had the one way valve, but i removed it)....all i did was loop it up and to the back of the mounting it higher over the chain(the end pointing down)...so in theory it would act as a chainluber (hahaha, i know its silly, but, why not).
so the question is.....IS THE PART WHERE THE WHITE HOSE GOES IN, the Crankcase Breather....and what should be the NORMAL things i should see...
at the moment....it blows a bit of smoke...and drips a bit of oil, at speed. and i guess it sucks up water when kickstarting with the end submerged. (its NOT the water pump seals....i have golden oil when it pointed UP and away from water)
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That must be a newer 250 than mine. My bike does not have that powervalve vent. I have a Yz125 that has that powervalve breather. The crankcase breather hose is the vent hose that comes off of the top of the transmission. Usually the carb lines are clear (stained brown) and the cranckcase hose is smaller and black. The hose you are pointing out there, comes from the powervalve. My 125 that has the same breather hose, drips oil and puffs a little smoke, too, but I cannot tell you the purpose. I do know the factory has it mounted to the frame pointing down and mine does not suck water on the yz125. Its definately not crank seals leaking, but could be a seal or gasket in the powervalve assembly. :wink:
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Well, thank goodness.....its the POWERVALVE BREATHER!!!!!
that coughs oil and sputters some smoke......
THANK YOU THANK YOU THANK YOU...
sorry guys for the missinformation....i was talking about the Powervalve Vent not the crankcase breather....
i feel much better....
sheeew!!!!
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Something has to come out of the gearbox to actuate the PV. That means that the gearbox is somewhat open to the PV. The exhaust creates a lot of vacuum so i can see it sucking in water. If the current routing of the hose is working for you IMO you will be good.
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When crap starts coming out of that vent I'm pretty sure that means it time to clean the power valve.
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You will get abit of dripping and smoke out of the PV vent tube, its normal. My 04 and my girls 07 do it. You may get a little bit of condensation also. My old 01 and 02 YZ250s also dripped from the PV vent.
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This is GREAT NEWS...
expect some dripping and smoking....CHECK!
CAN suck in water....CHECK!
New routing should be fine....CHECK!
I am sure this solved like 5 different issues in one GO!
Thanks so MUCH!
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I have my vents routed down like the factory had them, otherwise it wont vent/drain properly. That black goo will end up collecting in the cover.
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yeah, i thought that there wont be enough pressure to blow the goo out...when i had the hose pointed straight UP.....but low and behold....i had a dirty boot/ dirty pant / dirty radiator and a dirty motor....so its blows with some force, I am sure...that i would get it to go OVER the motor, and out the back.....which i point down, so the last bit of the "draining" action....gravity could help out.
Attached is a image / diagram of the extension and the tip where it "spits"....right over the chain.
i attached the "stock" hose with the L bend to the frame.....the L pointing Back....and added the white hose from the POWERVALVE to the top of the Stock hose.
and whenever i end the ride....i close the petcock....and burn the last bit of fuel in the carb....so maybe...that would also blow out the last bit of goo in the pipe....or i can just remove the white hose from the powervalve it self....and blow it clean like that?
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sorry i have been away for a few days. right as the other guys say it is your pv vent. as it is blowing and sucking i would say that some of the seals are not working. i can not think of any damage that would result from runing it in this state as long as the water is kept out (PLEASE CORRECT ME, ANYONE). i would say the best thing to do is wait until your next top end over haul and replace anything then. i have included a diagram of a 99 250 barrel not the same as yours but you can get an idea of what needs to be done.
regards john
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Cool thing is....i have a 2 year Factory Warranty on my bike.....and i plan to rebuild it twice before it runs out :P
i mean....MAKE them rebuild it....then, i'll make sure EVERYTHINGS covered.
and i know, i AM dubious about dealer/stealer warranties.....but, i have to say, these guys are pretty good, they even replace the fork seals when they start weeping.....only place in SA that has a warranty like that....so, i am sure they will cover everything needed.....
paid top dollar for it.....and well, after the "HUSABERG INCIDENT" i will never ever buy a 2nd hand bike without a warranty. (AND NEEEEEEEVER EVER buy a 4Stroke...okay maybe a KLX450)
thanks for the heads up Jonny.....i will make sure to be critical when they do it.