Thanks for taking the time to read this and forgive me if it's been discussed before but my searching skills have let me down.
Let me start by saying I've been back to the stock muffler for a while now and have noticed over a year or so that my factory muffler has developed a chirp, wistle or kazoo like symptom. It goes away under hard throttle but in normal operation it's quite noticible. Has anyone else endured this sound that is right out of the Jetson's?
There are no leaks at the muffler gasket or holes that I've noticed.
With regards to your chirp, check that the metal decorative LHS vertical cover plate is not vibrating against the main body of the silencer, as it is only fixed at the front and rear.
Its the ribbed cover in the above picture behind the black pipe.
but I fixed it by jamming a couple of S/S washers in between it and the silencer body, in the middle of the silencer (top and Bottom).
- hope you get what I mean.
It cured my chirp / metallic zing on the ER6 box (that I was gutting the cat on) when I first started it up
Maybe that is why it was sold cheap to me
Thought I had not tightened something up at first when I revved the engine on no load. It sounded rattly / zingey compared to my original Versys exhaust.
I initially found it, by putting a flat blade screwdriver that I was prodding things to feel / find the chirp / zing, and put up between the plate and the silencer body and it stopped it.
Anyway this solved my problem, but just saying this is another thing it could be / check / discount.