High pitch resonace @ ~ 3500-4000 RPM?

Hello All,
I brought this up a while ago, but the thread was sidetracked by me. So, my bike is still producing a high pitch resonance that is coming from the the engine. Upper near the valve cover. The cam chain tensioner has been adjusted, valves done to spec, all plugs caramel at all positions of throttle, etc. I have it running like a sewing machine. Carbs clean and synched as well. While pouring over the forums someone mentioned something similar and it was a damaged front cam chain guide.

First I want to take off the valve cover and pull on the cam chain to check tautness, was going to do that today, but it was raining, the engine was still hot after a test ride and it was muggy in the garage. So, I'll have to get that tomorrow. I keep my bike in my parents garage (live in an apartment), so I can't go and do this now. I'll include video for sound.

My question tonight is if anyone has had this happen and what is the procedure to replace the front guide without dismantling if there is one. Also, what are the signs to look for with failing guides. 1981 XJ550RH Seca. This is something I could use your wealth of knowledge on, Fitz, so any help you could provide would be much appreciated.

Thanks

PS - Here is the link to the other post: http://xjbikes.com/Forums/viewtopic/t=29669.html

It contains pictures of the cam chain and top guide if it helps.

 

Have a look in the fiche: http://www.yamahapartshouse.net/pages/O ... brand=YAM#

Under "camshaft-chain" and you'll see that the front guide is retained by a small plate ("washer, spec'l shape") with a bolt and washer at the top front of the head. Access to the front guide's retainer is as easy as removing the valve cover gasket.

 

Pulled the valve cover. There is only about a 1/16th - 1/8th inch slack in the cam chain and no evidence of fresh scoring on the underside of the valve cover. Tach cable was also disconnected and sound remained. Repacked tach cable while off.

Here is the link to the video of the bike running and the mystery sound: http://www.youtube.com/watch?v=Gpg3geJaY3I

 

The thing to do is PINPOINT where the sound is coming from.
Easily done.
"Probe" for the Noise.

Use a Long Dowel, Fiberglas Driveway marker, Mop or Broom Handle.
An object that you can place one end on the Engine and "Listen" to the other end.

A 4-Foot length of Fiberglass Rod Driveway Marker with a Golf Ball drilled and epoxied on-the-end is the livin'-end.

Run the Bike.
Put the Probe to the Mill where you think you should listen.
"Listen" to the Probe by putting your ear to the Golf Ball.
You should hear Normal ::: "Machinery Noises and Rotational Sounds"

When you Probe the spot where the Noise is emitting from; you'll distinctly hear it and can zero-in, ... right on-the-spot.

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The Video isn't the best way to locate the squeal.
But, if I had to Buzz-in and make my answer in the form of a question.

"What is a loose Oil Pump Gear Cover?"

"What is a loose Clutch Splash Plate?"

 

Mystery Sound Solved
The sound was actually the carb heat shield touching the case and at a specific resonance it made the high pitched shrill. When I held the heat guard of the case the sound didn't occur. While I had the carbs off afterwards, I bent the shield some so that it doesn't touch the case anymore and I haven't heard it since. Glad to know it was benign. It did come in handy though, it got $200 dollars knocked off the price when I first bought it!