K11 Blown Cylinder?

[diesel]

Hello Fellow Brickers, hoping you can advise. I was flying my K yesterday afternoon on the way up to my brother's cottage (long, flat, quiet regional roads perfect for trying to achieve top speed) when suddenly something broke.  I immediately lost power and the sound of the engine changed slightly, but the bike continued to run pretty well and I kept riding for about a half hour since I was in the middle of nowhere. I mean, it sounded a little rough at low revs when I pulled away from a stop sign but otherwise nothing unusual, temperature gauge was steady, fan continued to go on and off and no signs of blue in the exhaust. My first thought was that I'd lost a cylinder and obviously was hoping it would be spark or fuel related as apposed to valves, pistons or rings. I pulled over at a gas station near my destination and when I turned the key off some dribbles of oil trickled down on the left side and heated up on the exhaust causing a smelly smokey scene for a few seconds. There was plenty of crankcase oil in the sight glass, so after re-fueling I started it again. There was a cloud of blue smoke for a few seconds then it went clear, the bike sounded fine otherwise so I rode the remaining 10 minutes to my destination.    Any ideas what could have gone? The fact that it didn't leak any oil until I turned the motor off suggests a leak in an area where there's vacuum or suction happening, but I don't really know what I'm talking about (I'm no wrench). Wondering if there's any possibility of nursing it home on 3 cylinders. It's a 3-4 hour drive.
Thanks All!

[Laitch]

Wondering if there's any possibility of nursing it home on 3 cylinders. It's a 3-4 hour drive.

I think it's unwise to keep riding. It could be as simple as the crankcase vent tube disintegrating or more troublesome like a blown head gasket or worse. Continuing your ride may make accelerate the defect and ruin the engine. If you have time and ability, you should try to find the source of the leak and post a photo here.

If you're willing to risk being stranded an hour or two after you start out again and with worse damage than you have now, go ahead. Taking risks and winning can be exhilarating.

[Motorhobo]

I'm no trained wrench either so I'm sure someone will have better advice, but for starters:

When you say something broke, do you mean you heard something physically break with a loud noise and the sound of something falling or some impact, or was it just that something changed suddenly?

If the former, then I'd try to figure out what physically broke before riding it. In either case, you said you have oil drippage. I would first try to determine the source of that leak, assuming it wasn't there before, and whether it is engine oil or transmission oil, and how much it is. If it's engine oil and the oil level is still normal, that's good. If it's transmission oil, I'd check the transmission oil level and final drive gear oil level before continuing. I'd also check the coolant level and check under the water/oil pump for seepage for good measure.

If your fluids are OK and you have no serious leaks, I'd be looking for the cause of the power loss. First, I'd pull the cover off the spark plugs and make sure none of the cables are bad. While idling, pull the wires off one by one and see if the idle changes. If the idle doesn't change when one of the wires is off, then that is a bad wire and you're running on 3 cylinders. I'd say it's OK to ride with 3 cylinders for a couple hundred miles. If it's not that, then you have another issue that is affecting power output -- but if all your fluids are topped off and stay stable, I personally don't know of any damage that could be done to an engine over a couple hundred miles at freeway speed running on 3 cylinders or with a vacuum leak that results in a performance drop but doesn't cause the engine to cut out or run exceptionally rough.

[The Mighty Gryphon]

Have you tried to start the engine since it cooled off? 

When you say some oil ran down the left side, was it while the bike was on the sidestand??

When you start the cold engine, does it start readily and idle smoothly?

Are there any noises coming from the engine?

I am suspecting the crankcase breather hose is cracked or has slipped off a fitting. 

A broken breather will lean out the mixture slightly and leak a small amount of condensed oil vapor.  Hose failures are pretty common on these bikes given their age.

I am more familiar with the K75 Jetronic system than the Motronic system on your bike, but I am pretty sure there is a means for pulling crankcase vapor into the cylinders.  A failure in that system could give the symptoms you are seeing.

As far as riding, if you can find the leak a temporary fix would be to wrap it with electrical tape.  In any event, unless the engine is making unusual mechanical noises I would tend to think it should be good for a couple hundred miles of easy riding.

[diesel]

Thanks everyone for your help! This morning I took the seat off and the lower cowling, there was very little oil collected there.
Traced the trickle from the top of the crankcase right where it meets the transmission. It's very oily around the bottom of what I think is the air cleaner housing. To answer MG's question, yes the bike was on the side-stand at the gas station when I turned it off and the oil started to drip.
Haven't started the bike yet today, standby.

[diesel]

Just ran the bike for a few minutes, seems to be running fine except for the blue smoke. Still dripping around the air cleaner housing joins.
Otherwise it sounds normal running on the centre stand.

[diesel]

Here's a picture of what I think is the leaky area.

[diesel]

Sorry about the orientation, you'll have to crook your head to the left.

[Laitch]

You haven't answered a question you've been asked. When you said "something broke", Motorhobo asked you if you heard something break. That's an important question to answer.

Is the blue smoke coming from the end of the exhaust pipe, or from somewhere else? Is there white smoke coming from the end of the exhaust? Do you have a working temperature gauge on the bike or just the warning light? Has there been any indication of overheating?

[The Mighty Gryphon]

It sounds to me like the crankcase breather.  I'm pretty sure your photo shows the "z" hose that connects the breather on the block to the airbox.  It looks like there is a slight smear of oil on the end of the hose. 

Those hoses are infamous for cracking and making the engine run rough.  Fortunately, it is one of, if not the only piece of rubber that BMW sells that isn't stupidly overpriced. 

Riding the bike with that hose cracked will be a bit messy with crankcase blowby, but I wouldn't think it will destroy your engine.

[Laitch]

It sounds to me like the crankcase breather.  I'm pretty sure your photo shows the "z" hose that connects the breather on the block to the airbox.  It looks like there is a slight smear of oil on the end of the hose.

Installing that part is more involved on the K1100 than on the others. It requires opening the air box, but it could be the cause of the problem, or it could be indicating other problems, too. Maybe all that's happened is that it has broken apart where it passes into the air box. The groove that anchors it is visible in the attached photo.

[The Mighty Gryphon]

I think the hose in question is #10 in this drawing

[diesel]

Thanks again everyone for all your assistance. My apologies to Motohobo for not answering the question about something breaking. (and thanks Laitch for the reminder) In truth I didn't actually hear or feel anything break, just a sudden loss of acceleration and change in engine sound. There was a lot of blue smoke when the bike was restarted at the gas station, but initially the blue smoke was burn-off when it trickled down the side. I had already ruled out coolant issues, the temp gauge works like a charm, fan comes on and off regularly. Lot's of oil in the crankcase, also checked the transmission oil it was golden and just below max. All of these factors pointed us towards a breather/hose leak theory.

Motobrick is such a great community. My brother and I were working through all the great advice you gave while reconciling them with our own assessments based on our experience and what I felt while riding the bike for another 40 miles after the initial "break". It was interesting to me that it didn't noticeably leak oil until it was turned off and on the side stand. We were on the same page as Mighty Gryphon and felt redeemed by his crankcase breather prognosis. Not wanting to take the tank off and risk breaking pressurized fuel lines, I drove the bike home this afternoon/evening, apart from lacking power and growling at low revs on what seemed like 3 cylinders it performed admirably. I did have to add oil along the way as it was blowing a lot. It would stall occasionally when decelerating for a red light, luckily there were only a few of those on the entire trip. Now that it's home I can figure out how to get at it.

[Laitch]

I think the hose in question is #10 in this drawing

I thought that too, at first, Gryph, but I think BMW is using a generic engine diagram and putting the specifics in the parts lineup. This long hose is #10 and illustrated in the parts list that accompanies the diagram. There is no z-hose in the lineup but we know BMW still makes and sells them.

[Laitch]

Now that it's home I can figure out how to get at it.

  :clap: Now wasn't that exhilarating?

You'll need to remove the air box and open it up. It will all become clear. Here's the post that shows the layout.

[diesel]

Exhilarating?! Maybe a little. Thanks for the pics, I guess I have to take that tank off don't I?

 

[Laitch]

Exhilarating?! Maybe a little. Thanks for the pics, I guess I have to take that tank off don't I?

Well, you can always try doing it without removing the tank.

A BMW workshop manual or Clymer manual reveals many things. Just take off the tank, wrap it up so it doesn't get dinged and proceed. Take photos for reference as you go and post up your progress in this thread with photos. While you're in that area, check all rubber components for integrity and replace the elderly ones—replace them all if you've got the inclination and money.

There's a complete K1100LT/RS repair manual in the Technical Library Index. Go get it.

[Vespa no more]

Ah... always interesting to stumble upon an answer...

Picked up a 1983 K100RS a couple of weeks ago. Upon starting the (reluctant) bike, there was the white smoke out the exhaust. Seemed like it needed a good long run.

Having a look around the motor (air intake box was off) could see oil building up fairly quickly on top. Turned motor off.

So my guess is that it was the crankcase ventilation tube broken or missing.

Fingers crossed.

Bike is still sitting at my mate's place

[bikesnbones]

Hello Fellow Brickers, hoping you can advise. I was flying my K yesterday afternoon on the way up to my brother's cottage (long, flat, quiet regional roads perfect for trying to achieve top speed) when suddenly something broke.  I immediately lost power and the sound of the engine changed slightly, but the bike continued to run pretty well and I kept riding for about a half hour since I was in the middle of nowhere. I mean, it sounded a little rough at low revs when I pulled away from a stop sign but otherwise nothing unusual, temperature gauge was steady, fan continued to go on and off and no signs of blue in the exhaust. My first thought was that I'd lost a cylinder and obviously was hoping it would be spark or fuel related as apposed to valves, pistons or rings. I pulled over at a gas station near my destination and when I turned the key off some dribbles of oil trickled down on the left side and heated up on the exhaust causing a smelly smokey scene for a few seconds. There was plenty of crankcase oil in the sight glass, so after re-fueling I started it again. There was a cloud of blue smoke for a few seconds then it went clear, the bike sounded fine otherwise so I rode the remaining 10 minutes to my destination.    Any ideas what could have gone? The fact that it didn't leak any oil until I turned the motor off suggests a leak in an area where there's vacuum or suction happening, but I don't really know what I'm talking about (I'm no wrench). Wondering if there's any possibility of nursing it home on 3 cylinders. It's a 3-4 hour drive.
Thanks All!

Amazingly, this is a carbon copy of what happened to an RS I once owned, including the fluid leak.
I was accelerating onto a dual carriageway when it happened.
Pulled over to have a look and found coolant all over the exhaust.
I limped it home on three cylinders, and took the plugs out.
The plug from cylinder two had completely melted.
There was no electrode left.
I did a compression test, which showed zero.
When I got the head off, there was a pronounced dent in the piston, and the bore was toast.
Hope you're luckier than I was.