My 850 sings in B flat! Why?

I hear a harmonic ringing sound that does not change with engine speed or gear I'm in. I mostly hear it at around town speeds but it may be happening at freeway speeds to but be drowned out by other noises. It does sound like harmonic vibration but I don't know. I remember some post about rubber pieces to dampen vibration of the heads cooling fins but no such post found in a search. Don't remember them on Nortons, could this be the cause? Thanks. Glenn

Pre-ignition? poor petrol??
Cash

Do you use the locking tabs on the exhaust nuts,they also ring quite freely

You may be on to something. I recently tightened my exhaust nuts. I do not know if there are locking tabs. I have never had them off of this bike. What do they look like? As for pre ignition or bad gas, wouldn't that sound change with engeion speed?

gtsun said:

I hear a harmonic ringing sound that does not change with engine speed or gear I'm in. I mostly hear it at around town speeds but it may be happening at freeway speeds to but be drowned out by other noises. It does sound like harmonic vibration but I don't know. I remember some post about rubber pieces to dampen vibration of the heads cooling fins but no such post found in a search. Don't remember them on Nortons, could this be the cause? Thanks. Glenn

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Yep, my vote is also for exhaust nut lockrings! Mine sang pretty loudly until I got rid of them.

gtsun said:

I recently tightened my exhaust nuts. I do not know if there are locking tabs.

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As you have tightened the exhaust nuts, then you probably would have noticed if the locking rings were fitted, because one pair of tabs should have needed to be straightened before you could turn the nuts?

Once the nut has been fully tightened with the lock ring in place on the nut thread, it is positioned so that the narrow pair of tabs can be bent to locate onto a cylinder head fin, and the opposite pair of tabs bent either side of a nut fin. If both pairs of tabs are not pinched tightly against their respective fins, then they will rattle, and they often loosen after a while anyway.

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My hearing loss is pretty bad so I suppose what I hear and what others do may well be different.That said, when I hear that ringing noise a change to 97/99 octane or a couple of degrees less timing gets shot. I do not and never will use locking rings on the exhaust nuts, IMO the quickest way to ruin the threads in the head, I'm sure they'll ring though.

Cash

After looking at the parts book I determined I do not have locking tabs. (thanks L.A.B.) However I tried a few other things the noise seems to be gone now. #1 disconnected the speedo cable thinking the Gage may have been making the noise. I've seen this on much older bikes. Did nothing. Next I put several silicone high temp rubber pieces between the fins at the very front of the head as it sounded like it might be the fins "ringing". At the same time I rearanged the tach & other cables & wires coming up the front frame tubes because I had recently taken my front end apart to paint, put in new steering head bearings & change to clippons etc. I did a good test ride & the noise seems to be gone. May still be very slight but not the howl as before. Today I will take the rubbers out & see what happens. Thanks. Glenn.