Engine noise sourced to exhaust

[legaleli]

I was pretty sure I had engine issues with both of my bikes - a sharp scraping noise (almost a clacking noise) that came from both engines depending on load and engine temperature but whose cadence rose and fell with the engine rpms. While looking for the source I realized that if I squeezed or put down pressure from my riding boot on the left side exhausts the noise would diminish or in some cases go away together. That lead me to think that the pipes were either major "telegraphs" of the engine noise, or they were somehow directly involved. I took them off and reassembled them looking for where they were hitting th frame or loose in connection - everything SEEMED fine but the noise persisted.

I then hit them with a rubber mallet looking for a source and that's when the "Ah HA" happened; if I banged on the 1 and 2 pipes of BOTH bikes (coincidence) I get a buzzing from their connection to the exhaust port. 3 and 4 pipes are a good snug fit with no rattle. In other words, when I fit pipes 1 and 2 into the cylinders at the exhaust ports and tighten the bolts snugly and evenly there is still room for the pipes to rattle; maybe the seals are toasted. I guess the noise is coming from the rattling caused by the pressure changes. I guess the changing nature of the sound over time is caused by the heating and cooling of the engine and pipe.

What is the fix here?

note: This may be asked and answered HERE at #2 - exhaust gasket. That said, I'd rather hear it form someone here than with me guessing on my own.

[Dave8338]

I'd start with new exhaust gaskets and go from there.

[Big T]

Be sure that you get the other end of the pipe inthe muffler, then tighten up at the head, then the pipe to muffler clamp

I know it sounds basic, but you should never be surprised at the dumb things previous owners do

[legaleli]

Time for a Z1 order it looks!