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Discussion Starter · #1 ·
1980 CX500D. Got the bike two years ago with about 24000 miles on it, and I've added about 1000 miles to the odometer. The bike is 99% original, runs great, has not yet overheated, or had any other issues.

On a recent non-interstate ride (temps = 50 - 60 F, max speed about 65 mph), I pulled over after about 40 miles to admire some of nature's wonders. As soon as I came to a stop, I noticed a noise coming from the front of the bike. It was definitely engine speed related, and I can best describe it as a whine. Sounded like a leaf had gotten into the fan (as it once did on a 68 VW). I shut off the engine, let it sit for a couple of minutes, and upon restarting the noise was gone. After riding a few more miles, riding at about 5500 rpm, I noticed the tach needle was bouncing (this was normal), but the temp gauge was also fluctuating rapidly (not normal). Both needles settled down as the rpm's dropped below 5000 rpm. Later the tach needle fluctuated again at about 5500 (normally settles down above 6500), but the temp gauge remained steady. BTW, normally the temp gauge rises to the beginning of the wide white stripe and stays there without much movement. On this day it also stayed there except when it fluctuated that one time.

When I got home, I read on this forum about some of the fan issues (can come loose, or blow apart and damage the radiator), and the water pump/mechanical seal issues. Could the whining noise be a fan issue? If the fan did come loose, could it self-tighten as you ride? Could the temp gauge fluctuation result from bike vibration, or a worn or failing tach cable? Could the whining noise come from the tach drive at the engine?

If this subject has already been discussed and problem solved, I apologize for the duplication. I wasn't able to find anything addressing my problem, except for one recent thread about a whine that might be an engine bearing.
 

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It is generally frowned upon to ask the same question in more than one thread. Signs/Symptoms of Cooling System Issues
I suspect that a moderator will merge the threads for you.

The most likely source of a whining noise is from either the tachometer or the speedometer gauges. The fix is to remove the instrument , turn upside down and put a drop or two of very light machine oil on the place where the cable attaches. Let sit overnight.

If the tach needle is not very steady that could indicate that the cable needs lubrication. See the factory service manual which you can download from the Wiki ( see link in my signature)

The temperature gauge shouldn't fluctuate very much. I'd suspect a bad electrical connection.

If the bolt securing the fan is loose it will not self tighten. You may be able to check that by tilting the rad forward and reaching in behind to the fan. To do that you would have to remove the mounting bolts.
 

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I don’t think the noise is related to the ten gauge. You should check the 7volt regulator that the temp gauge is plugged into. I would also pull the fan and check it’s condition( cracks around the hub).
 

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Could the whining noise be a fan issue? If the fan did come loose, could it self-tighten as you ride? Could the temp gauge fluctuation result from bike vibration, or a worn or failing tach cable? Could the whining noise come from the tach drive at the engine?
I gave this answer on your other thread on the same question Symptoms of Failing Fan or Water Pump?

The whining noise is most likely from the tachometer or speedometer.

If the fan comes loose it will not self-tighten.

It is not likely that the temperature gauge is fluctuating due to vibration and is in no way connected to the tach cable. The whining noise is more likely from the tach itself rather than from the drive at the engine. Try lubricating the tach cable.
 

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'84 CX650E that is evolving into a GL500
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Discussion Starter · #8 ·
Yes. Sorry. I didn’t realize a post had to be reviewed. I had posted the one, but didn’t see it when I looked about an hour later. So I thought I pushed the wrong button. Old school at it worst.
 

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Discussion Starter · #9 ·
Regarding the noise, I took off the tach and lightly lubed the drive and the cable with PB Blaster garage door lube. Went for a ride for several miles and both tach and temp needle rock steady at all rpm’s and the whining noise is gone.

But after reading up a bit more about the CX cooling system, and especially the fan life, I think I will remove the radiator to inspect the 40 year old fan. I will also replace the coolant. What is the correct coolant mixture to use?
 

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'84 CX650E that is evolving into a GL500
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Posts do not have to be reviewed before appearing unless the software decides they look like spam. But sometimes you can't see it because your browser shows what the page looked like when it loaded it recently instead of what has changed since then unless you refresh the page (hold the shift key while you click the reload button).

Perhaps the vibration from the tach cable's lube being hard was making the temp gauge bounce?

You may find this useful: CX/GL500/650 Cooling System Servicing:

BTW: Please add your location to your profile and your bike's model and model year to your signature (see Forum Settings link in my signature) so that you don't have to tell us every time and we don't have to ask when you forget.
 

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Discussion Starter · #12 ·
Bob, your post is very informative. Regarding coolant, a website called Motofaction states that "Honda recommended a 50:50 mixture of ethylene glycol and distilled water". Do you agree or should another solution be used?
 

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'84 CX650E that is evolving into a GL500
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As I said in the article, regular ethylene glycol based coolant mixed 50:50 with water is fine.
I suppose if you had a source of plain ethylene glycol you could use that but it is a lot easier to just buy the stuff they sell for use in cars.

Compatibility with brass radiators and aluminum engine blocks used to be a concern but just about any coolant you can buy these days is compatible with all metals.

BTW: They used to dye coolant fluorescent green to help with finding leaks. When auto makers started experimenting with different formulations they dyed them different colours so that mechanics & vehicle owners could tell if they were adding the right product. In recent years I find that most glycol based coolant is a pale yellow, barely different from plain water and I have trouble seeing the level in the recovery tank so I have been adding a few drops of blue food colouring when I mix it with water to make it visible.
 

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Regarding the noise, I took off the tach and lightly lubed the drive and the cable with PB Blaster garage door lube. Went for a ride for several miles and both tach and temp needle rock steady at all rpm’s and the whining noise is gone.

But after reading up a bit more about the CX cooling system, and especially the fan life, I think I will remove the radiator to inspect the 40 year old fan. I will also replace the coolant. What is the correct coolant mixture to use?
When you reinstall your fan, be sure to use a torque wrench and torque to 14-18 ft-lb.
 

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Discussion Starter · #17 ·
Yesterday began my first attempt at removing the radiator to inspect the fan for old age/stress cracks. So far I’ve removed the metal outer radiator cover and the plastic radiator “guard”. I’ll post some pics later today.
 

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99.999% chance you will find cracks around the hub. I removed a fan I installed less than a year prior and was cracked. I didn’t use a torque wrench when I installed it and very likely over torqued it. The consensus on this forum seems to be that it’s very unlikely to remove a fan and not find a crack.
 
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