While riding my CB350F, I notice a high pitch nails-on-chalkboard noise at about 5400 rpm when accelerating. It seems to happen in multiple gears-- happens in 2nd and 3rd frequently, didn't try 1st, 4th, or 5th much. It seems like it might only happen when accelerating but I'm not sure. It will happen at the same spot, probably 5400, and then continue through another constant spot, maybe 5600 and then stop once I accelerate faster. So, if I accelerate slowly through this range, it lasts longer, while a fast acceleration it's just a 1/2 second noise. It's pretty loud, loud enough to notice it, and I hear it from my left ear, which makes me believe it's coming from the left side of the engine.
It doesn't always happen, but I can't find much of a rhyme or reason to what may make it happen or not. I wasn't able to get it to happen after I was going 50 for a few miles so maybe it goes away when the engine's warm, but I am not sure of that yet.
Any idea what this could be?
