Did you change your coolant recently?
Stick a screwdriver on you waterpump and see if that's where your whisling is coming from.
I had that issue and the Honda coolant made the whistle go away. Don't ask me why. The whistle had started after my coolant change without Honda coolant even though it was a (compatable coolant).

 

No, the coolant hasnt been changed recently. I thought about the water pump, but the fact is that it only happens when the engine is hot. The water pump is turning as soon as the bike is running, so that made me think vacuum.

 

Yep, when hot and especially at idle was when mine would do it. If it does it at high speeds it could be the hole in the top of your axle. If the hole is pointed up just wrong it is like blowing a whistle.

 

The only place to start is to isolate the location of the noise. I usually use a piece of some type of hose and put one end in my ear then move the hose around the engine.

 

Humm, only at idle, even louder when hot. Air leak would make the [head to carb] boot expand even more, if I'm thinking air before carb, it's gotta stall leak wise.

Makes me think sonic vibrations? Cover the air intake opening by hand, just to upset the harmonics? Or say the boot cover on the air cleaner side is not mounted over the lip of the carb, that squeak of a sonic there?

Are we 'earing' the pitch out of the pipes? Say a spackle knife acts the guillotine and upsets the harmonic there? Unless you can pinpoint to any mods done, i.e., not stock, something recently removed and replaced?

A video if it perhaps?

 

All stock. The air breather is under the seat....I can put my ear to the seat to see, well, hear LOL. I will try to post a video soon....

 

Is 17 kind of wheezing at idle? Most of those parts are not listed, and I'm not saying 17 is it. Just saying it's hard to diagnose over the net. More like spit balling something that would cause and effect.

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My 750 ACE would whistle also only when hot & at idle, as soon as you give it some gas it would go away.
Replacing the water pump fixed the issue, now I only run factory type coolant in my bike, as I believe the Prestone caused an issue with mine

 

My 750 ACE would whistle also only when hot & at idles

OK, I'll buy it. Now, tell me is that ambient like a heat wave, or in the fall, no snow yet but feels like. Should be any day the bike is at its full heat cycle, ambient does not matter. It's pick a day, month, etc.

as soon as you give it some gas it would go away.

Boy, I'm about to call that normal.

Replacing the water pump fixed the issue

Let me get this straight... I'm thinking, no mechanical seal leak to change out the pump. No oil out the same seep hole being the pump shaft seal to water pump. And no coolant change back to the OE, and the jobber (prestone) they use in their bottles [assuming], but now the hindsight of not knowing if the coolant [alone] change would cure it?

And now we have rseneff with a 98, who knows how long that was changed, or prestone calls it, he changed up how long ago, rsen? What a time to find out. Past two years since last done, then off to a Honda dealer for a bottle or two, the junk science is on!

Just saying, does not go away with the coolant change, and no leaks/overheats caused by it(?), I do not ride idling. Get it! Normal.

 

That’s my story & if you don’t like it tough sh!t

Oh, I said I'd buy it. I just wanted a more of a conformation WHY. YOu justified the change out. Thank you... But 25k later it was still salvageable when the leak stopped?

That's how stout and robust the mechanical seal is. So you swayed from using OEM, and dare you go. That should teach the house.

That's still puts this thread in limbo without rseneff stating he swapped out to non-OE, or never changed the coolant.

RSEN??

 

Squirt some wd40 into weep hole ....

 

Put a rag over the end of the pipes to see if a leak at the flange gaskets could be the cause. Spray carb cleaner around the carb boots and hoses to see if it is a vacuum leak there.
Vacuum is high at idle.

 

As mentioned, do the hose listening method to isolate the the noise. Should be elementary from that point.