1988 Honda GL 1500 Gold Wing "high pitched sound goes away" Questions

high pitched squeel. Not load but annoying. As I rev the motor up the squeel gets higher with the RPM's also I shut the motor off and try again and most of the time it goes away. The timing belts were

...high pitched whistling sound at idle a vacuum leak or what? My vt750c recently began to whistle loudly at idle when fully warmed up. Whistle goes away when idle is increaesd by throttle but not when ...

...likely a high pitch sound especially when you let off is a vacuum leak, or leak around your airbox. Off the throttle the engine is at maximum vacuum. Look at hoses cracked or not properly pushed ...