Crankcase Breather Hose: Help

[Tlaw1994]

I am looking to replace the crankcase breather hose (looks like a Z)on a 91 K75RT. A dealer quoted me one and a half hour in labor to do this. Do you need to take anything out to access this hose? It appears to me all you need to do is loosen the top and bottom clamps, remove and replace the hose. Is there something else I am missing? I dont think you need to drain anything either.

thank you for any insights.

[kbasa]

I am looking to replace the crankcase breather hose (looks like a Z)on a 91 K75RT. A dealer quoted me one and a half hour in labor to do this. Do you need to take anything out to access this hose? It appears to me all you need to do is loosen the top and bottom clamps, remove and replace the hose. Is there something else I am missing? I dont think you need to drain anything either.

thank you for any insights.

That's it. Nothing fancy, but it's kind of a pain to reach.

Those hoses seem to lead a hard life.

[bikerfish1100]

it's a nuisance job- but nothing technically difficult. pretty much just nuts & bolts, and somewhat time consuming. plan to change your air filter while you're in there, if it's anything close to due.

[98lee]

Changing the hose is a ten minute, one screw driver, two hose clamp job IF you have screw type hose clamps on there now (not the crimp type) AND the lower rear of the fairing is not in the way.

I've changed 3Ss and one RT and none took more than ten minutes and:

11151460480 vent hose $14.62

Now it is possible that the RT had the left fairing lower removed (I don't remember. It wasn't my bike).

Do it yourself and do it soon. You will be pleased at how much better it will run (if it is currently cracked).


:dance :dance :dance

[Tlaw1994]

thank you, everyone. I suspected it should not take longer than 10 to 15 minutes. I will report back the actual time and effort once it is done. The part is on order.

[PHMarvin]

What dealer quoted you 1 1/2 labor hours to replace the breather hose on a K75 anything? Unless it was a mistake (unlikely), he deserves the name, "stealer".

[BuddingGeezer]

You need to look at the thread "Throtle Problem" in K Bikes. Paul glaves explains why the crank case vent hose should be plugged.

Ralph Sims

[98lee]

BuddingGeezer:

I think you are thinking of the vent hose that vents the gas tank into the crankcase.

This thread is about the !/2" dia. "S" shaped hose that vents the crankcase in to the
throttlebody plenum.

All vehicles must have the crankcase vented (whether it be to atmosphere, the induction system, or the exhaust system) to relieve the build up of pressure in the crankcase. non-venting would cause seals to blow out.

On the otherhand, the venting of the gas tank into the crankcase, is not such a good idea, as it adds even more fuel vapor into the oil. While the bike is running, this vapor gets sucked into the induction system through the above mentioned "S" hose.
But, when the bike is sitting, especially in the sun for hours (like 8 hours at work), the expanding vapors from the gas is slowly diluting your oil.

BMW vented the tank to the crankcase because they were trying not to vent tanks into our atmosphere. (I think it had something to do with the brown air the people in Los Angeles were trying to breath in the '70s.)


:dance :dance :dance

[BuddingGeezer]

As the church lady on Saturday Night Live would say, " Never Mind"

Ralph sims

[98lee]

BTDT.:thumb



:dance :dance :dance

[DrPaul]

As the church lady on Saturday Night Live would say, " Never Mind"

Ralph simsActually, it was Anna Rosanna Dana (Gilda Radner). I'm sure you were just a little tike back then!:brad

Paul

[jcridge]

"Isn't that special".....The church lady

[bikerfish1100]

Actually, it was Anna Rosanna Dana (Gilda Radner). I'm sure you were just a little tike back then!:brad

Paul

and for fans of Gilda who like things notated correctly, Gilda's character was Roseanne Roseannadana. Her musical cousin was Carlos Santana Roseannadana. You know Jane, it's always something.

http://i132.photobucket.com/albums/q13/bikerfish1100/MOA%20rallies/Gilda_Radner.jpg

[DrPaul]

and for fans of Gilda who like things notated correctly, Gilda's character was Roseanne Roseannadana. We have medications for this problem now...... :p

Dr. Paul

[dswilliams47]

You will be pleased at how much better it will run (if it is currently cracked).


Why would a cracked vent hose cause the bike to run poorly? It just moves air in and out of the crankcase doesn't it? No vaccuum, pressure, or fluids are involved are they?

Dave

[PGlaves]

Why would a cracked vent hose cause the bike to run poorly? It just moves air in and out of the crankcase doesn't it? No vaccuum, pressure, or fluids are involved are they?

Dave

To quickly observe how the engine runs poorly with the crankcase not sealed just remove the oil filler cap and watch the engine try to idle. You will notice that it does a really crappy job of running with the crankcase open to the atmosphere. I've never bothered to try to figure out the physics of it: just the fact that it won't run well was good enough for me.

Try it - you'll see!

[lostboy]

The crankcase vent hose enters the plenum chamber downstream of th airflow meter. Any extra air allowed in through cracks in the hose are "unmeasured" by the airflow meter, causing a lean condition.

Other leaks into the case can also lead to lean running: A missing oil filler cap, or one without an o-ring, very loose valve cover bolts, or broken grommets under them, etc.

[dswilliams47]

Thanks for the input. I've noticed the bike stumbling lately and I have some oil deposits around the butterfly valves. I guess today's project will be to pull the lower fairing, find the breather hose and see if it's the problem.

Dave

[dlearl476]

Why would a cracked vent hose cause the bike to run poorly? It just moves air in and out of the crankcase doesn't it? No vaccuum, pressure, or fluids are involved are they?

Dave

I don't know if it's as critical on a K bike, but I had a very knowlegable Ducati mechanic explain to me how the crankcase breather and vaccum induced in the manifold "trick" the engine into thinking the CC has a greater capacity than it does, and its a kind of "harmonic balance" that's important not only for the crankcase pressure (think about it, the bottom side of the pistons produce compression as the piston comes down, just like the top does as it goes up) but the manifold pressure as well.

And as Lostboy noted, if the inlet is downstream of the meter, it would be even more critical than that, producing a "lean" running condition.

[lostboy]

Another problem caused by a cracked crankcase vent hose is that it allows water into the case when the bike is run in the wet. I've seen bikes with so much moisture in the motor oil that it looked like a nice milkshake.

[dswilliams47]

Boy, I'm glad I checked it out. My breather hose was dried and cracked with a large gaping slit at the bottom connection. That's obviously where all the oil blow-by was coming from. I wrapped the hose in black electrical tape for a temp fix and tomorrow it's off to the stealer to pay $15 for a 5" rubber hose.

Dave

[lostboy]

Be glad you don't have a K1/K1100!