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Classic K? Change Your Breather Hose

ted

Dum vivimus vivamus
A friend bought a K75C some time ago and I coached her on what parts to buy to bring it back to life. She sold the bike before we could do much of the work and I inherited the parts (including a breather hose and clamps...) So this afternoon I was going through my parts bin and decided that even though it was supposedly just changed 12k miles ago, it is such an easy job I might as well knock it out. I grabbed my tools, aka a long shank flat head screwdriver, and headed out to the bike.

It looked great, maybe a little dry rotted around the neck but nothing to worry about, here is a pic of it removed, as it looked on the bike:

breatherhose_1.jpg


I loosed up the hose clamps and popped off the old one, and was pretty surprised at this:

breatherhose_2.jpg


Yup - that harmless and very minor dry rot was actually a tear going about 2/3 around the entire neck. I popped the new one on (making sure to orient it correctly and load the hose clamps first) and screwed it in. Planning on a ride tomorrow morning, hoping it will ride even nicer :)

So, moral of the story, spend the $20 and replace yours next time you are working on the bike - takes all of three minutes!
 
This was part of my annual maintenance on the K1100LT... el crapo rubber means this pieces cracks/tears yearly.
 
NOT a dumb question. The only dumb ones are the ones that go unasked.

The hose vents crankcase pressure into the back of the intake plenum just above the throttle bodies. Any crack in this hose allows unmetered air into the throttle bodies causing a lean condition.

I am not positive how visible it is on an RT with the lowers installed. It is a black 1/2-3/4" diameter Z shaped hose (See Ted's picture).

It is on the left side of the engine to the rear of the throttle bodies and ahead of the coils. It is in behind the black plastic Throttle Position Switch that is on the right end of the throttle shaft.

I hate to make any negative comments about one of our best parts suppliers, but, unless he has changed suppliers or the supplier has upgraded his product, DO NOT buy the reproduction sold by Beemerboneyard. The quality of this particular reproduction is even worse (thinner and with very noticeable weakness at the mold lines). Their price is only $9 vs BMW's $15.20, but if it's going to fail more often, there is a net negative savings. I don't fault Beemerboneyard for trying to get a more cost conscious solution for our common problem, but in this one isolated instance their supplier came up short. I continue to look to Beemerboneyard for MANY huge savings on new (master cylinder rebuild kits, oil filters, etc) and used parts for our bikes. They are a first rate source for early K parts.



:dance:dance:dance
 
I changed mine last year just because it was 24 years old. It was stiff, but no cracking or splits. I'll keep it and see how the Beemboneyard replacement holds up. Since it's not a stressed or highly pressurized part, the thickness might not be an issue as much as the compound.
 
I changed mine last year just because it was 24 years old. It was stiff, but no cracking or splits. I'll keep it and see how the Beemboneyard replacement holds up. Since it's not a stressed or highly pressurized part, the thickness might not be an issue as much as the compound.

If it's already in the bike, I would keep a much closer eye on it than in the past and when it fails (they ALL do, OEM or not) replace it with OEM.



:dance:dance:dance
 
Here is the best article there is on the Internet for chasing down and fixing air leaks:
http://k-technik.pytalhost.com/pdf/Falschluftopt.pdf

Too bad it is in German :) That said, Google Translate does a good enough job that you can get the general idea. Note that in the piece the bottom hose clamp is turned around backwards which would make removing that hose a few hour job rather than the 10-minute job it should be as you would have to remove the airbox to get to it - check yours first.

The hose itself has a specific top and bottom. Remove the one on there by loosening the hose clamps, moving them to the middle of the hose then just popping off the hose. The new hose is a bit tricky to get on, but goes right on if you go slow and steady. Start with the bottom piece, it takes a little english to get it over the metal nipple and firmly seated all the way down, just go slow and avoid any temptation to use the screwdriver to inch it down. Small hands help :)

Once you have the bottom on open up the hose clamps all the way and slip them onto the hose, oriented so you have clear access to the tightening screw once the clamp is in place. Getting the hose clamp onto the bottom part also takes a bit of patience (and small fingers help) but you'll be able to slowly get it all the way down over it. Make sure it is all the way down else you'll pinch at the top and split the hose while tightening. Once the bottom is done, the top is easy.

Lastly, as long as you are replacing the breather hose (pn#11151460480) and hose clamps if needed (pn#1151460935) you might want to also replace a few more easy and inexpensive things that also go bad, including the oil cap o-ring (pn#11141460674), vacuum hose (the one inside the spring - pn#11727545323), and the bleed nipple caps (1 per cylinder - pn#13547694924).
 
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"""The hose vents crankcase pressure into the back of the intake plenum just above the throttle bodies. Any crack in this hose allows unmetered air into the throttle bodies causing a lean condition."""


I'm confused, (its easy to do) if it is crankcase pressure being vented back to the intake, wouldn't it be 'unmetered' anyway. Isnt this just an 'pollution control' hose like on a car motor? Or does it enter the intake circuit before the 'airflow meter' or whatever it is called. And also, why isnt this hose routed 'before' the air filter. Isn't this situation just pumping dirty carbon/oil filled air into the combustion chamber?
 
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COLOR="Red"]The hose vents crankcase pressure into the back of the intake plenum just above the throttle bodies. Any crack in this hose allows unmetered air into the throttle bodies causing a lean condition.
[/COLOR]

I'm confused, (its easy to do) if it is crankcase pressure being vented back to the intake, wouldn't it be 'unmetered' anyway. Isnt this just an 'pollution control' hose like on a car motor? Or does it enter the intake circuit before the 'airflow meter' or whatever it is called. And also, why isnt this hose routed 'before' the air filter. Isn't this situation just pumping dirty carbon/oil filled air into the combustion chamber?


Yes, it is there because the days of Road Draft Tubes ended around 1963.

Since your crankcase is basically sealed from incoming air, all that hose is supposed to do is keep pressure from building from heat and what goes by the rings. That small amount is accounted for in the fuel mapping of the computer.

On the other hand , if there is a crack in the hose, OUTSIDE air is introduced after the air flow meter throwing off the mixture.

If it was routed before the filter or the air flow meter, it would trash the filter or the air flow meter. There is lots of oil mist coming out of there.





:dance:dance:dance
 
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