Engine Oil Leak at Breather Hose - K-Bikes.com - Excellence in Motion
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post #1 of 9 (permalink) Old Aug 18th, 2008, 2:49 pm Thread Starter
The Fllash's Avatar
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Engine Oil Leak at Breather Hose

I found an oil leak at the crankcase breather hose that connects at the rear, top center of the engine. This hose goes to a plastic manifold that connects to all the throttle bodies.
The hose has a crack in it close to the fitting on the engine.

I had complained to my dealer about this oil leak one year ago, just before the bike had reached the end of the warranty. The dealer told me I had over-filled the crankcase oil and charged me $100.00 to do a half-ass cleaning job.

The bike is a 2004 K1200RS with 33,500 miles.

In order to replace the hose you have to remove the throttle bodies. The service manual has good instructions for this remove and replace. I hope the replace goes easy.
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post #2 of 9 (permalink) Old Aug 18th, 2008, 4:14 pm
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Hmm, I'm starting to suspect I have one of these problems too. I'm at 84,500 miles. I started seeing oil seep from the top of the crank cover about nine months ago. It's gotten progressively worse, so I bought a crank cover gasket a couple weeks ago, but haven't gotten to replace it yet. Now you've got me wondering if its the breather hose. This would also explain why I get a bit of "coughing" when the bike is cold, it may be running too lean. I'll look into it tonight.

Thanks for the tip.

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post #3 of 9 (permalink) Old Aug 7th, 2011, 4:21 am
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Crankcase breather hose leak

Thanks for the info you have posted. It has been very helpful.

I have a 1999 K1200RS with 101,000km. After fixing leaking rear seal and camshaft cover I still had an oil leak around the head at the top of the motor.
Research on the net let me to conclude that the likely cause was the crankcase breather hose. I disconnected the breather from the crankcase and removed the throttle bodies. This revealed that the manifold pipe was split in 2 locations. This caused oil to leak all over the top of the engine making a big mess.
The job looked a bit daunting but removal has not been too difficult. The throttle bodies come out quite easily once the wiring is disconnected. Then the throttle cable can be removed.
Once I have the new parts then its the assembly. I am a bit concerned about reconnecting the breather to the crankcase. Any advice would be appreciated.
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post #4 of 9 (permalink) Old Aug 7th, 2011, 5:08 am
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Not sure where your concern is. On these Efi computer managed engines, the system assumes there is closed circuit breathing and makes compensations in the fuel air mapping. If you don't have it then I suspect something will stay out of balance.

Your only concern should be putting back a hose that might split again at some future date. The consensus is, we don't think much of the material chosen for the oem hoses in that location, but since they are molded to shape you would probably have to get some hose connectors and silicone hose to do a better long life job.

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post #5 of 9 (permalink) Old Aug 7th, 2011, 11:36 am
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It is more difficult to replace the hose than to remove the old one, but is doable with long needle nose pliers and a long screw driver for the screw clamp. Since you have everything off, it is much easier though more involved than just doing the crankcase end alone. The factory clamps are the compression/squeeze type. Not many of us have the tool for that and thus have resorted to small screw clamps for the attachment to the back of the throttle bodies. As Voxmagna has said, the material is not the best. I am on my third or fourth - one was nicked by the dealer when they did one and so it failed prematurely. So, be carefull in those tight spaces, don't nick the rubber with a screwdriver and I ended up only replacing the angled part coming out of the crankcase to the plastic tube joining the two sections. Use a nut driver if you can get one long enough to reach. Once done, you will have solved your oiling problem and the bike will likely run a little better after getting rid of the leaks on the back side of the throttle bodies.

Jim Douglas
'00 K1200RS >135,000 mi, '09 K1300S sold @ 22,232 mi
'93 K1100RS traded up @ 78,000 mi, '85 K100RS sold @44,000 mi, Kawi 650 track bike - sold
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post #6 of 9 (permalink) Old Aug 8th, 2011, 1:51 am
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I managed to reuse those 'special' clamps by closing them far enough that I could just slip them over the throttle body rubbers before assembly. Then it was simple to squeeze them closed with a pair of long nose pliers. They close with a distinct 'click' when you get it right and seem to have a simple 'barb' to ensure they stay closed.
To replace the breather hose, the throttle cables can be left attached and the whole unit swung up and away to gain access. This is helpful if you have cruise that has very sensitive adjustments. Simply use a bungy cord to keep the throttle bodies up and out of the way while you work beneath. I was als concerned about the crank case end of the breather as it is almost more awkward than the other end! But a pair of needle nose pliers and a little patience and it was no problem. 100000km and I am on my original breather and its still soft and has no signs of perishing. At least when it does go I will be quite happy going in there again. Clymer is a must have!
I also flicked the centre throttle return spring off its retaining pin, loosening up the throttle a bit following other posts on the matter. Worth doing. The whole exercise also helps us to understand what is down there as for years I looked at the area and, apart from a bit of a clean, was happy to leave well alone.

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post #7 of 9 (permalink) Old Aug 8th, 2011, 2:25 am
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i just completed the same job. it's tedious, but was very rewarding. my bike idles slower now no doubt due to the consistency of vacuum. leave the throttle cables alone, simply roll throttle body 45 degrees for access and attach all 4 nipples. i pulled the fuel rail for better access. a good long needle nose at the crankcase will shove the hose right on. like i said, tedious but rewarding.
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post #8 of 9 (permalink) Old Aug 14th, 2011, 7:40 pm
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Gonna JB Weld my pipe... Not because I'm cheap but it will work better vs cracking in a few years or few K miles. Honda has had us JB up cracked cylinder blocks with success.
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post #9 of 9 (permalink) Old Aug 14th, 2011, 8:37 pm
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The "special tool" can be bought for $20 at most auto stores.

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