K11 Owners Group

[Jim]

Just ran across this on another K bike site:

"For the most part, the smoky exhaust on startup is a problem common to nearly all motorcycles and nearly no automobiles because cars do not have separate oil tanks that sit above the level of the motor and most motorcycles do. In a car engine, all the oil is stored in the oil pan under the motor and is cycled to the engine and returned to the oil pan. Every thing remains the same, even over time.

Where as on a motorcycle, the oil is usually stored above the engine in a tank. Over time when sitting, oil leaks past the mechanism intended to retain the oil in the tank i.e. Ball Check or Close tolerance of the pump dive, or what ever. The leaked oil all finds it's way to the lower end where the space is insufficient to hold all of it so it fills to the point that when started, the crank or flywheels as the case may be, picks up so much oil and flings it up into the bores that the rings can't deflect it fast enough so the oil smears past the rings and gets burned in the combustion chamber.

Eventually, the oil pump cycles the excess oil back up to the tank and the smoking stops. The Preferred way to handle the condition is to drain the lower end of the engine hopefully via a drain plug and manually return the oil to the tank. Any time you have oil getting past your rings and burning out the exhaust, you are oil fowling your spark plugs and adding a thick layer of soot to the combustion chamber and valves. All this carbon takes many miles to burn off and actually never does. These deposits build up into a cake that deforms the intended flow pattern of the head and becomes a glowing carbon igniter that sets off the gas charge prematurely causing detonation; a condition that can be rephrased as your fucking motor eating itself alive.

All the situations mentioned by you guys are variations on the same theme. The side stand problem is the same thing but only effecting one side of the motor. The moral of the story is, if you don't start you bike for a month or two, it's a good idea to drain the lower end before starting and pore it back into the oil bag."

Or maybe I should have posted this in the Dungeon...
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Jim
1997 K1100LTSE 94,000 - has gremlins!
1995 R100RT Classic 16,650 crashed - repairing
1992 K75RTP 46,000

"We shall not all die, but we shall all be changed."

[flybd5]

Round aircraft engines have the same issues with oil collecting in the cylinders. It's why they always get their props turned manually, or the starter engaged with the ignition off; to get rid of that oil which could damage the engine if there is too much of it and the pressure builds. Another solution is to remove the plugs from the bottom cylinders and drain the oil, but that isn't always feasible, such as in the case of a DC-3 or B-17 (I used to work on one of those in a museum in Fort Worth).

But the issue with fouling is easily dealt with on aircraft -- you lean the engine to increase temperature in the cylinder and any deposits are burned off quite rapidly. Unfortunately, our bikes have no such manual mixture control.
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To err once is human. To do so repeatedly is incompetence.
1995 K1100LT SE

[Flying Duck]

The reason K bikes smoke on startup is that the cylinders point downward when the bike is put on the side stand and the oil behind the pistons seeps past the rings. You can mitigate this by turning off the bike and tilting it to the right for a few seconds to let the hot oil behind the pistons drain back into the sump.

The only thing I've had foul plugs is letting a K bike idle for a long time. For some reason are K75s most prone to this occurring.

And remember that K bike BMW manuals recommend riding off right away once you start the bike, not letting it sit and idle to warm up.

K1100 rider manual - Page 42:


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93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
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