1994 K75S High-pitched chirping noise when hot?

I'm getting an intermittent but fairly loud high-pitched chirping noise from somewhere under the tank when the bike gets hot.

The radiator fan seems to be working OK and the chirping is independant of that; only thing in common is that it only occurs when the bike is running hot (now living here in Albuquerque that is much more often than my previous location where I first noticed it several months ago).

I suspect a bearing somewhere; perhaps the water pump is acting up?

If anyone can shed some light on what my problem might be that would be great. Hopefully it's nothing serious, but...

Regards, Jeff

Jeff - your best bet - visit a Harbor Freight and purchase a mechanic's stethoscope. That should let you localize it.

"Under the tank" is a wide expanse of territory to guess where the noise is coming from. It could be anything from a bearing going bad somewhere, to the a plugged fuel filter (the fuel pump has a blow-off valve that chirps when it's pushing against too high a resistance.)

Try to narrow it down a bit and get back to us with your findings.

[QUOTE=Zagando;801441]I'm getting an intermittent but fairly loud high-pitched chirping noise from somewhere under the tank when the bike gets hot.

The radiator fan seems to be working OK and the chirping is independant of that; only thing in common is that it only occurs when the bike is running hot (now living here in Albuquerque that is much more often than my previous location where I first noticed it several months ago).

I suspect a bearing somewhere; perhaps the water pump is acting up?

If anyone can shed some light on what my problem might be that would be great. Hopefully it's nothing serious, but...

Regards, Jeff[/QUOTE]

Just so I am on the same page with you, does it ever chirp when the fan is not running?

Yes, it chirps when the fan is on or off; doesn't make any difference.

It always seems to happen when I am riding or at a stoplight and only when things are hot (ambient temps as well as the bike all warmed up in stop and go traffic.

Maybe no need for a mechanic's stethoscope as I happen to have a medical stethoscope on hand (I was Dr. Mango Daiquiri come Halloween at my last job (bartender)). Perhaps it will come in handy again so I'll start carrying it with me when I go out on the bike.

Thanks, guys!

FWIW, my '87 K75s whined this past week when stopped at a traffic signal with the fan trying to keep her from overheating.

Heck, I was whining too!

Let's not confuse the whining of the fuel pump with this intermittant high-pitched chirp, please! Definitely out of the ordinary in my K-bike experience.

[QUOTE=Zagando;801763]Let's not confuse the whining of the fuel pump with this intermittant high-pitched chirp, please! Definitely out of the ordinary in my K-bike experience.[/QUOTE]

In case you misunderstood.. the fuel pump is capable of putting out 100PSI, until it burns up or explodes IF the output is plugged up (say by a bad fuel filter.) To prevent this from happening, it has a built in blow-off valve. That valve kicks in at about 80 PSI, and when it relieves the pressure, it sounds like a chirp. As the pump keeps running, it then sounds like a series of chirps. THAT is what I was referring to - not the normal whining noise (although that does get louder as restriction builds on the output of the fuel pump.)

It's not a common noise - but it is a known noise. It may be out of the ordinary in your K-bike experience, but it is not out of the ordinary for everyone's k-bike experience.

YMMV.. (but not a lot.)

OK, Don, Thanks for that explanation. I was referring to Ken's post immediately preceding mine, though; not yours.

There is the fuel pump whining which we're all accustomed to but this is an almost screeching, slightly warbly chirp. On and off, usually for as long as twenty seconds or as short as 2 or 3.

From what you describe it very well could be that fuel pump pressure relief valve. It would certainly be worth my while to replace the fuel filter ASAP and see if it goes away. If not then I've at least eliminated one possible cause.

With it occuring only when it's hot out that might make the most sense, too---I can often smell gas fumes when I'm sitting in traffic or at a light. The pressure must be all the more intense in these summer conditions.

Thanks again and I'll let you know when I get a new filter in the tank.

Don, where do you get this technical information? Wow! I am impressed (no sarcasm implied AT ALL) by the troubleshooting knowledge of some folks in this forum. :thumb

Zagando, let us know if the stethoscope idea helped and the outcome. You should videotape the noise and post it for our own experience...ok, I am pushing it a little. :wave

I saw a stethoscope at Sears and [I]almost[/I] went for it.

Chirping? Does your bike still have the SHED emissions system installed?

If you raise the back of the gas tank out of its rubber holders, there may be a hose on the right-rear side with gray-colored valve attached to it. You don't want that part there. :D

[QUOTE=deilenberger;801774]In case you misunderstood.. the fuel pump is capable of putting out 100PSI, until it burns up or explodes IF the output is plugged up (say by a bad fuel filter.) To prevent this from happening, it has a built in blow-off valve. That valve kicks in at about 80 PSI, and when it relieves the pressure, it sounds like a chirp. As the pump keeps running, it then sounds like a series of chirps. THAT is what I was referring to - not the normal whining noise (although that does get louder as restriction builds on the output of the fuel pump.)

It's not a common noise - but it is a known noise. It may be out of the ordinary in your K-bike experience, but it is not out of the ordinary for everyone's k-bike experience.

YMMV.. (but not a lot.)[/QUOTE]

That is [I]very[/I] interesting information. Is that true of the later style K-1100/R-1100 fuel pumps?

[QUOTE=jdiaz;801858]Chirping? Does your bike still have the SHED emissions system installed?

If you raise the back of the gas tank out of its rubber holders, there may be a hose on the right-rear side with gray-colored valve attached to it. You don't want that part there. :D[/QUOTE]

Don't think I have one of those at all; I probably would have noticed something like that in all of the times I've taken off the tank for one reason or another---but thanks for the the thought, nonetheless.

I'll get over to a local Napa outlet later and get a new fuel filter later today. I just discovered that it's been almost three years since I changed the FF so it can't hurt even if it's not at the root of the problem.

Regards, Jeff

[QUOTE=Zagando;801957]Don't think I have one of those at all; I probably would have noticed something like that in all of the times I've taken off the tank for one reason or another---but thanks for the the thought, nonetheless.

[/QUOTE]

Do you have ANY hoses attached to the two vent ports at the right rear of the tank? Or do you have the "cup" (air accumulator) attached to the frame directly underneath these two vent ports with no hoses connected to the right rear of the tank?




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Only the little cup, Lee---no hoses.

:thumb



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