Topic: What is making that terrible sound near redline?

[bistromath]

Another "mystery sound" thread! 

My '75 550F makes what can only be described as a "ringing" sound near redline, coming from the head somewhere. Like, it sounds great all the way up to 6-7K, and then it starts making a sound like an oven timer going off. Pulls hard, runs fine, idles great, but I'm thinking the cam chain is vibrating on something, or something. Tensioner works when I turn it (spring is stuck) and I've got it set halfway between a rattle and a whine, as they say. Whaddya think? Am I going to self destruct this thing if I keep whaling on it?

[lordmoonpie]

Is it like a high pitched erratic sounding whine at max revs?

It might be the girlfriend on the back then....

[Tower]

Uh oh..."Ask not for whom the bell tolls...as it may be tolling for thee..."  never mind, just kidding.

These bikes apparently make lots of disturbing noises.  At least mine does, as it seems so does yours.  Still, sounds quieter at high speeds than my old Triumph did.

[Jonesy]

Are the little white rubber slugs in place between the cylinder cooling fins?

[bistromath]

What? White rubber slugs? I don't remember seeing these on any SOHC4.... where are they located? What are they for? And what do they have to do with the noise I'm hearing?

[Jonesy]

A few threads have come up about these now and then. There are little white (or grayish) round rubber discs that are placed between every other cooling fin on the cylinders, along the front and back sides. They have little bumps on them to hold them in place to corresponding little holes in the fins. At higher engine speeds, the natural frequency of the cooling fins can be reached by the engine vibration and cause them to resonate, making a ringing sound. The rubber slugs cushion the fins and stop them from reaching resonant frequency.

Ooops... I just re-read your original post and see you have a 550... I thought I read that you had a 750, my mistake. I don't think the 550 used these. Sorry!