K1100LT constant pitch whine / scream

[Bluebeard]

Help please guys,
My K11 has a constant frequency whine, so bad it's quite annoying up to the point where the wind noise drowns it out.
It isn't there immediately on starting the engine but it's there after a few, maybe ten, minutes.  It stops if the engine stops, ie if I use the kill switch, but leave the ignition on.

My theory is that it's the fan, it is constant speed, not engine speed or road speed, so what else could it be?
Is the circuitry such that it will be controlled by the engine kill switch?
I also think that the thermostat controlling the fan must come in too low, because the engine isn't hot enough to bring the fan in.

Before I strip the bike down, I need it to go to work on Monday, does anyone have previous of this sort of thing?

BTW this is a magic site. My first time here, very impressed.

[rbm]

If it sounds like a swarm of buzzing bees, it might be the fuel pump.  Does the sound get louder with a low fuel level?  If so, that's another clue pointing to the fuel pump.  Consensus is that "they all do this", if you find out it is the pump making your noise.  http://www.motobrick.com/index.php/topic,2058.msg14179.html#msg14179

[Bluebeard]

Thanks Robert,

I started it up on the centre stand yesterday, and ran it up till the fan cut in. Nothing unusual there, a fairly normal fan noise.  And the cut in temperature is far higher than the engine reaches in this weather.  But the whine didn't start either. It is definately a whine, almost a shriek. I've got a complete spare tank off a K100, which I suspect is identical.  Next time I've got the stamina, I'll swop it over.

Ian

[rbm]

You're on the correct track with your diagnosis.  Try to isolate the noise between the fan or the fuel pump. I've had a shriek noise on my K100 in the past and it turned out to be the fan.  Possibly, the best remedy at the moment is to remove the fan, examine it and try to service it.  The sleeve bearing at the front is the primary failure point, since it gets peppered with road dirt and tends to seize.  Lubricating the bearing tends to address the symptom but does not cure the cause.  I once saw  that a K-bike owner took J-B Weld and covered a spot on the radiator directly in front of the bearing.  The reason he did this was to repair damage done to the rad when the fan blade ground its way into the rad fins, but it subsequently protected the bearing from direct road dirt.  If you apply preventative maintenance on the fan at this point, you can simplify the diagnosis if the sound reappears after the service.

[Qdude]

Could air pressure/wind be a contributing factor?

You said that you started it on the center stand and there was nothing unusual, but that was not the condition that produced the whine... no "wind tunnel effect".

You might isolate the fan whine possibility by disconnecting the fan power, then riding it to try to get it to whine. No fan power, no fan whine when electrified with wind tunnel air pressure.

Just a thought. I like to eliminate as many possibilities as possible when searching for a gremlin in the system...

Best of luck. 

[frankenduck]

Or you could pull the tank and find the fan connector and jump it. (Brown is ground, the pother one's positive.