Video here: http://s1198.beta.photobucket.com/user/Dydler/media/sound_zpsb0dd26e1.mp4.html

Note -- the noise levels are really skewed from the compression. It's loudest at about a 45 degree angle off the top of the cylinder head, slightly audible at the lower end, and pretty quiet everywhere else. Also, bike is only running on left cylinder to give it a bit more load (see below).


Quick info, I have much more if needed -- Been running like this approx 2,500 miles without significant change.

Last work done before this started was valve check about 800 miles prior. Have adjusted the valves after the noise started and got no change.

The noise is loudest under slight load and with the engine cold. Most obvious between 3.5k-5k RPM. Additional load seems to make it go away. Once it warms up it's still there at about half the volume and rev range.

Shorting the left spark plug out stops the noise.

Noise frequency is 1/2 the RPM. Happens reliably and consistently within rev/load range.

High octane gas seems to have very slightly helped. But turning the choke on does not at all (noise only goes away when engine starts misfiring from being way too rich). I may be imagining it.

Putting left cylinder on downstroke and pushing piston with rod yielded no motion.

Been through very wide range of temperatures, altitudes, and jettings with no change to the noise.

Bike idles perfectly at 3 turns out, runs great, no loss in power.

Camshafts have enough play to rattle them around by hand with the cover off.

Changed from 10w40 to 15w40 diesel oil, no difference.


There's also an accompanying noise that sounds very similar that only appears at idle once completely warm and fades out as the bike revs to 2000 RPM. I've pinpointed it with a stethoscope to be loudest on the spark plug and the area around the spark plug of the left cylinder, getting quieter in every other direction. Right cylinder does not make the same noise.


Any help would be appreciated. This noise is an annoyance that I want to get rid of for good.

suggestion # 1 :i would check and make sure that the exhaust gaskets are seated squarely and exhausts are tightened at the head.suggestion #2 i would check that the spark plug gasket is in place and a little stone has not found its way under the gasket as they can find there way into the spark plug recess if you are not carfull when you remove plugs ,also check plug tightness. Last suggestion is to check your head gasket is not leaking ,the head bolts on this moter are recomended to lossen and retorque every 4000 miles . MY 2 CENTS WORTH

Exhaust gaskets were replaced about 1000 miles ago. Spark plug seats are good.

Head gasket leak -- possibly. I've spend about an hour on youtube going through head gasket leak sounds and there don't seem to be many. This is probably closest I've found to the sound my bike is making: http://www.youtube.com/watch?v=U8JJmGZdMlQ

So if it is the head gasket, should loosening and re-torquing the head noticeably change the sound? I did check the torque about 1000 miles ago, but I didn't loosen them and none needed tightening so they didn't move at all.

a head gasket leaking makes a chirping sound ,thats the nearest i can desribe it .when it finaly lets go you would know it.i would say exhaust gaskets cause they have probably settled in . (compressed). the reason that you loosen the head bolts is that they freeze with use and you dont get a false torque reading. if you put a torqe wrench on your existing bolts you probably would get a higher reading by 4 or 5 lbs or more  before you even got faint movement.. this is the only bike ive ever owned that ive had to do this with. though others out there have probably come  across others..

I don't believe it's the exhaust gaskets. Throughout the noise occurring I've retorqued, replaced, and retorqued again, no change in sound.

I suppose I'll get my hands on another torque wrench when I can afford one and retorque the head as you described and see if that changes anything. Thanks for the suggestions.

Just loosened and re-torqued, no change in sound. New Iridium plugs and zero resistance wires too. Since it's not getting worse I'm tempted to say %$*# it and just keep riding it as it is. In the meantime, any other ideas?