smoking NOT a side stand issue

[Ocelot]

First of all, let's get past the side stand issue. Let's assume it's NOT oil seeping past the rings because she's parked on the side stand. What we are not looking for here is yet another dose of "TADT park it on the center stand."

1988 K75 with 48k on the clock smokes at start up like a smudge pot. The owner can ride a while, park on the center stand for a few, fire her up, and she smokes; so it's not just when the engine is cold. After strangling all the skeeters for a quarter mile around, the smoke clears away and she runs just fine. Smoke does not smell like coolant. Oil clean. Doesn't lose fluids. Plugs toasty. Runs smooth and strong.

This bike was recently brought back to life. Clean injectors, new hoses, new fluids, replaced pump seal, etc. Didn't used to smoke when first brought to life. Getting worse.

So I am posting this question for the owner, who is not much of a poster: What should we check for? What else would make smoke at startup?  :dunno

[motodude]

Is the smoke blue (oil) or black (rich fuel mixture)?

Does it smoke more on acceleration or compression braking?

How long does it smoke before it clears up?  From cold?  From hot?

Tom

[Ocelot]

Smoke color is grey. Does not smell of coolant, does not lose coolant. 20/50 oil. Does not happen every time. Happening more often.

Smokes just starting. Don't know that he has checked acceleration versus engine braking . I will advise him to.

Have not timed how long it smokes. I personally only saw it do so cold. Seemed like it smudged for a darn long time.

I have asked him, next time it smokes, let it run until it stops, then turn off and check his plugs. Ought to be able to guess something from whether the plugs look sooty or wet.

[frankenduck]

Turn the bike off and then tilt it to the right for 15-20 seconds before putting it on the center stand to let the oil drain back into the sump. If it's an 88 then its got the old rings.

Also try compression testing to see how the cylinders are doing.

[thebob]

The obvious cure for this 'feature' is to mount the sidestand on the other side!

[Ocelot]

Well that's just a puzzle, thebob. Given the propensity of the boxers which preceded the brick to smoke from the port jug for the same reason, exactly what prevented BMW from mounting the brick the other way round, with its head on the starboard side? Instead, they made the situation even worse by leaning it so far over on a short side stand that the engine winds up fighting gravity and losing.

By the way, TDADT. Ocelot, for example, has never even once smoked at start. I always park her on the side stand immediately. Annie, my R1200CLC, has perhaps smoked twice in eighty thousand miles; and never since the engine finally completed break in. She has no center stand. They don't all do that. They don't. I personally believe the way to prevent it is to ignore instructions and break the engine in hard. First thing I did with Annie, on the way from the dealer new, I headed for the hills, with Bearswatter on back, where I twisted that round rubber thing hard. You don't need to spin fast; but you do need to pull hard. When I bought Ocelot, I specifically asked the original owner how he broke her in. Hard, he said. You want to buy me a new oilhead today, I'll break her in for you so she never does that. You have to seat the rings with pressure.

However, I digress. Frankenduck et al, I hope there is a way we can get past the "TADT park her on the center stand" known issue and consider instead what else may be causing this? Let's assume we've got that side stand business covered and it's not that. What else could it be?

I sent my buddy Motodude's three questions:

• Is the smoke blue (oil) or black (rich fuel mixture)?
• Does it smoke more on acceleration or compression braking?
• How long does it smoke before it clears up?  From cold?  From hot?['li]
  

Here's what he replied:

"Smoking appears to be oil smoke. Smokes on start up. Side stand or center stand makes no difference. Can smoke from a few seconds to a couple minutes. Once it stops does not smoke while running."

Not exact point by point answers, however, RIF, ya know.

Great weekend coming up. Going to camp in upstate NY, beside Lake Conesus. Friend of mine holds a chromehead wrechfest there annually on his old farm. I am hot to trot.

[thebob]

As long as we know that it is not overfilled with oil, there are really only 2 ways for oil to get into the combustion chamber.

Past the rings, or through the valve guides!

I'd try a compression test.

If the thing had been standing for a while, and then brought back to life then possibly the old oil had settled to sludge, but it has now found it's way back into suspension in the new oil, and has gummed the rings.

I'd try a compression test.

You could try a very long hard ride then an immediate oil change with a flush before refilling.

It's just an idea, but I cant think of anything else.

[Chaos]

Mine does the same thing, smokes even if on centerstand, but not always.  I'm guessing it partly depends if a piston stops with the valves closed and can develop a vacuum as the engine cools and draw oil in the compression chamber, but that's just a guess.  Things that help....tilt the bike to the right after shutting down as previously noted......keep the oil level in the bottom third of the sight glass....and, last but not least, it is most likely to smoke if people are watching and you are showing off your fine piece of German engineering.  When nobody's around the thing will start cleanly. 

[frankenduck]

Once you've turned the bike off, tilt it to the right for about for about 10-15 seconds before putting it on the center or side stand.  This lets the oil behind the pistons drain into the sump and reduces smoky startups.

[Duc750]

Is it allowed to idle a lot - these things run super rich at idle - I believe I read that on here as there is no air temp sensor - other question would be does it have the ALtitude plug on it ? SOunds more like "rich smoke" than oil smoke. One final one - could it be contaminated fuel or more specifically a contaminated fuel filter ?

[frankenduck]

Is it allowed to idle a lot - these things run super rich at idle - I believe I read that on here as there is no air temp sensor

Yeah, if you let them sit around idling long enough they'll foul the plugs.  Owner's manual suggests to start it up and get riding. No need to warm up the engine.

Correct.  No air temp sensor, only a mass airflow sensor.

[Inge K.]

A picture of the air temp. sensor at the AFM intake port.
(I`ll guess we`re still speaking about a `88 K75....???).



Inge K.

[Ocelot]

We talked it over after handball tonight . Settled on a good dose of Marvel Mystery Oil and flush. Will report back next week.

D

[Inge K.]

Is it allowed to idle a lot - these things run super rich at idle - I believe I read that on here as there is no air temp sensor

Yeah, if you let them sit around idling long enough they'll foul the plugs.  Owner's manual suggests to start it up and get riding. No need to warm up the engine.

Correct.  No air temp sensor, only a mass airflow sensor.

A picture of the air temp. sensor at the AFM intake port.
(I`ll guess we`re still speaking about a `88 K75....???).



Inge K.

How about it duck.........was we still speaking a `88 K75 ...........or did I misunderstand something?
Or did you smoke something that evening?    ..........just curious.

Inge K.

[frankenduck]

I've looked at many MAFs and never seen one of those. :dunno

If the point of your post is to "call me out" then it's really not necessary.  I've never claimed to be anything more than a shade tree mechanic who's been playing with these bikes for a while.  I've parted out many and brought a few of them"back from the dead" and picked up some hands on experience along the way.   In case you haven't noticed, most, if not all, of my write-ups contain a disclaimer that I'm not a professionally trained mechanic and what I post is just how I do things and what has worked for me.

I freely acknowledge that I am not an expert on engine management systems and that there's probably a host of people like Paul Glaves, Don Eilenberger, yourself and many others who know a lot more about the topic than I ever will (or care to.)  The L-Jetronic and Motronic are, for the most part, black boxes to me.

I've commented to the other mods about the vast amount of K knowledge you have and how it's great to have you on board and posting here because you really seem to know your stuff when it comes to K bikes. Your input here is greatly appreciated by me and I'm sure everyone else.

If I ever post something you know is wrong then feel free to point it out.  It's probably something that I can learn from. :2thumbup:

[Inge K.]

Thank you, for the encouraging words....start to feel that the ceiling touches the top of my head. :loopy:
Have followed your writings on the net for years, and always been amazed about your knowledge on the K`s.

I never thought that I teach you something related to K`s. :confused:
But it`s a good thing, when we all can learn a little bit from each other. :2thumbup:
My experience with this bikes is far away from yours, only some maintance and smaller
repairs during 26 years of ownership........but always been curious about how every small this
and that around the bike functions.

Small details are often easily overlooked, until the day they don`t functions as expected.
The air temp sensor at the AFM intake is present on every L-jetronic equipped K.
It is also shown in some wiring diagrams, on others the AFM is just a rectangle with four wires.

Green/Red: positive.
Brown: ground.
White/Red: air temp sensor signal.
White/Gray/: air flow sensor signal.

Inge K.