Update on Strange Sound... Still no explanation

Hey guys,

A while back I posted about a "Metallic Grinding Noise" that I thought was coming from the top end (only between 4-6.5k rpm). Many people suggested that I could have an exhaust leak. I removed pipes, banged em around, everything appeared to be ok... ran the bike without the pipes, still had the sound. Put em back on, did the RickoMatic "flag" check, no waving. Probed the bike with a screwdriver and listened for the noise... couldn't find it. Cam chain tensioner is good. No evidence of cam chain grinding against anything either (my fear).

I also checked speedo cable along with many other random parts of the bike with the probe, can't seem to find anything. The sound has matured a bit... seems like a bolt rattling around somewhere now. Fairing is off, by the way. I'm stumped. Really want to ride... can anyone offer any other things to check? It's super annoying and just appeared one day while riding. I was afraid it was causing damage, but now I'm just hoping that something is going to vibrate off one day and it'll leave me in piece (hopefully not a wheel or anything) :roll:

 

lol get the pun? Leave me in "piece"?

:lol:

 

does it run a bit rough at idle? check your carb boots, one of them could be sucking air.

 

I have a similar vibe/sound on my bike. Took me a long time to diagnose. It starts consistently right about 54mph and stops right at 61mph. It's done that for three years now....took me two to figure it out.

Try doing this: when you get the vibration/sound going good and strong, slide one foot in tight against the heat shield on the side of the collector box. The do it with the other foot.

My problem turned out to be that one of the welds on the ring clamp at the front of the shield had broken. So, it rattles in a certain rpm range and stops when you leave the range. For me it's right before 55 and just after 60. So, I've left it that way and I can hear when I approach 55 from either direction.
YMMV,

Dave Fox

 

Carb boots are good--- had them off and on while looking for the sound. Bike runs 100% fine. Going to check out the heat shield suggestion... thanks guys.

 

if you can't find the cause externally, you might want to pull your valve cover... i remember a post somewhere with similar symptoms and then the engine suddenly "seized", i think it was a bolt that came loose from the cam sprocket, jammed against the top of the head and kept it from spinning. the results are not pretty but also not the end of the world. if you open it up and find that this the case, make sure you completely degrease the parts and use threadlocker when reassembling (with new bolt(s) to replace the loose/damaged ones). definitely use the red stuff for the cam sprocket bolts. and it would be a good idea to pull the oil pan to remove the metal shavings - but only if you find things really messed as described above.

another thought, i suppose a loose cam cap could cause a rattling sound. again you would have to pop the valve cover to see.

thought #3, if you open the valve cover, check for oil, a blocked oil passage (or faulty oil pump) may cause things to "grind" if they are "dry".

let us know how you make out

cheers,

Trev

 

Thanks again for all of the advice.

Trev- I had the valve cover off earlier because I feared the cam chain may have been rubbing against something... everything looked ok in there, and I did an oil change this morning... no metal shavings or anything abnormal there either. I put it back together today and went for a ride (a good 30 miles). The sounds only comes between 4.5k and 5k rpm, which incidentally is the same range where I get a little bit of fairing buzz. I no longer think the sound is coming from the engine (after extensive probing w/screwdriver).

I would assume that if something was loose in the top end I would hear the sound over the entire powerband, and not just in a 500 rpm window? Is that right?

It really sounds like a loose nut vibrating... but don't think thats the case after ripping this thing apart and putting it back together.

I'm getting ready to just ignore it, but the thought of a seized engine is scary.

One other thing... the bike has begun to "mark it's spot" in the garage. Not sure if it's related, only maybe a drop or two after I've ridden.

 

I think there is a revved-up point, when the valves are tapping closed, combustions happening loudly, front and rear wheel zinging, middle gear whining, wind whistling through the wires and the exhaust note all decide to sing the same joyful tune in perfect eight-part harmony, ... when the Ghosts of all those who have motored over the road we're on want to join-in and add their appreciation for our enjoying that splendid moment and can only contribute in the one and only way they can by inappropriately rolling a tambourine and letting the jingles make us think there's loose parts rattling-around all-over inside the Plant.

It's Spooky!

 

Sniffle Sniffle.

Wipes tear from his eye.

That was beautiful Rick