high pitched whistle / squeal

[dntemp_ca]

Went for a ride today and my 78E developed a feint high pitched whistle....almost sounds like a squeal. At first I thought a brake was dragging, so I coasted to a stop and hopped off to touch the brake discs. Nope, not that. All discs were cool to touch. When I pull in the clutch and coast or rev the engine, the noise disappears. Seems to get louder as the bike heats up and at highway speeds. Any ideas?

[pgg]

Very mysterious - no mice hiding in the muffler? As the bike heats up, it's possible they start complaining? Just ignore me. Does it squeal when revved with the clutch pulled in? Maybe the small clutch bearing.

[pgg]

Sorry about the mice in exhaust system prognosis. It won't be the cause of squealing. Obviously hot mice will give more of a squeaking sound.

[Jerry]

Also check your middle gear oil level. Very common for you to hear the Hy-Vo chain at speed, but it should be more of a whir than a whistle. Check the header studs to make sure the nuts are tight; mine ned to be re-checked about every oil change. Last thing I can think of is that you have a vacuum line leak, check your hoses.