When I bought the 240 it had a 2000-2100 RPM rattle. I mentioned it here about two years ago and a solution was mentioned, but i never got around to it, just living with it. I finally had a few spare moments and remembered about the rattle (sort of like the old joke about the roof don't leak when it isn't raining). Sure enough, the suggestions were right.
the rattle is from the header pipe between the manifold and the resonator(?) in front of the catalytic converter. That pipe is double walled, but there is nothing between the two layers of pipe. As years go by, the heat/cooling cycles causes the inner and outer pipe to separate just a bit, and they get harmonic vibrations in certain RPM ranges. My solution was to use self-tapping sheet metal screws. I used
4- two in each pipe- one about 8" from the manifold and one about 8" from the resonator. I ran the full screw all the way in to cut the threads, then cut four off real short so they would protrude as little as possible into the exhaust flow.That did it! Took it for a test ride this AM, and what a relief! it's like driving a different car!
If I had a spot welder I would have just drilled a small hole and stick welded them together.