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A simple t’stat check is to start the cold engine and put your hand on the chrome water pipe. Within a few minutes the pipe should suddenly get hot, indicating the stat has opened as expected. This is also an indication the water pump is circulating coolant.
 

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If you have an IR temperature gun use that for some peace of mind.
 

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Discussion Starter · #24 ·
Thanks you all! I just ordered an IR Temp gun (15 dollars from Amazon) and it will be here tomorrow. I'll do the thermostat test by checking the chrome water pipe, and I will bust out my multimeter and see if the regulator is pushing 7v and ensure it's wired properly.

Anywhere in the wide white part of the scale is normal.
The narrow white part is low (I saw that a lot in the middle of winter but you probably won't except when it hasn't warmed up yet).
The red part is of the scale is red to warn you that the needle should not be there.

Note that internal combustion engines perform best when they are at about 95c(205f). Too much higher and things expand too much and can seize, too much lower and things don't expand enough to work properly plus the oil may not get hot enough to boil off moisture & contaminants.
Once I get the temp gun, my understanding is that I'll be aiming it at the engine block. Based on what I see from Sidecar Bob, I should be looking for a reading of about 95c/205f? If it's much hotter than that, I can then know that the engine is actually overheating and its not just an inaccurate temp gauge reading?
 

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Discussion Starter · #25 ·
OK, I can now report back on some things.

I got the bike fired up and confirmed that the 7v regulator is pushing 7 volts as appropriate.

I let the bike warm up and it appears that the thermostat is functioning - the water pipe got hot and was definitely moving fluid. I did notice that my reservoir tank was low, so I added about a pint of coolant to get it where it is supposed to be. Radiator is full.

What I did notice is that the fan has some kind of issue.

I allowed the bike to get hot and starting to approach the red zone. I looked at the fan and noticed that it was like, trying to start spinning. It was fluttering for a brief moment and then coming to rest, and then fluttering for an instant, and then coming to rest again.

Using a long thin object, I gave the fan blades a gentle prodding, and that seemed to allow the fan to finally kick on. It then fully engaged.

Once the fan was actively engaged, the temp seemed to drop and stabilize.

So, since the 7v regulator works, the thermostat is opening and fluid is moving, I think those things can be ruled out.

My question now is why has my fan been failing to engage? Maybe I need a new fan motor/unit?

I can say that out of the last 3 rides I've been on, I only noticed the fan kicking on once. The last two main rides (where the needle got to right next to the redline, the fan did not appear to kick on. Today it did, but only after seeing it flutter and giving it a gentle coaxing.
 

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OK, I can now report back on some things.

I got the bike fired up and confirmed that the 7v regulator is pushing 7 volts as appropriate.

I let the bike warm up and it appears that the thermostat is functioning - the water pipe got hot and was definitely moving fluid. I did notice that my reservoir tank was low, so I added about a pint of coolant to get it where it is supposed to be. Radiator is full.

What I did notice is that the fan has some kind of issue.

I allowed the bike to get hot and starting to approach the red zone. I looked at the fan and noticed that it was like, trying to start spinning. It was fluttering for a brief moment and then coming to rest, and then fluttering for an instant, and then coming to rest again.

Using a long thin object, I gave the fan blades a gentle prodding, and that seemed to allow the fan to finally kick on. It then fully engaged.

Once the fan was actively engaged, the temp seemed to drop and stabilize.

So, since the 7v regulator works, the thermostat is opening and fluid is moving, I think those things can be ruled out.

My question now is why has my fan been failing to engage? Maybe I need a new fan motor/unit?

I can say that out of the last 3 rides I've been on, I only noticed the fan kicking on once. The last two main rides (where the needle got to right next to the redline, the fan did not appear to kick on. Today it did, but only after seeing it flutter and giving it a gentle coaxing.
Check all connections especially the one at the fan switch at the bottom of the radiator. On mine I had problems getting a firm connection and ended up removing the big rubber plug and replacing it with 2 insulated female bullet connectors. Since then the fan kicks on correctly.
It may also be your fan motor that’s getting hard to turn. I don’t know if there’s a way to lube it.
 

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'84 CX650E that is evolving into a GL500
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Yeah, I'd start by unplugging the fan switch and seeing if jumping the connections in its connector makes the fan start or if it dies the same thing. If it still tries to move but doesn't move properly the fan motor is the problem. You might get lucky and be able to clean & lubricate it but you may be looking for a replacement.

If the fan comes on and runs at full speed as soon as you jump the connector the next thing I'd do is test the fan switch. The easy way would be to put an ohmmeter across it while the engine is hot and see if it is open (infinite ohms - the same as when the leads aren't touching anything) or closed (zero ohms - the same as when the leads are touching each other). If it doesn't read a steady & stable zero ohms when the engine is hot the switch is the problem.

4 cylinder GoldWIngs have a switch that is the same except for the thread size and people in the GoldWing community have reported taking the part of the switch that is in the coolant apart to clean things so they work again but I wouldn't trust that long term. There is a list of suitable replacements for the CX/GL bikes on the forum somewhere.
 

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Discussion Starter · #28 ·
So, yesterday I rode over to Nolimitz's place and we did a complete radiator drain and flush. On the way over to his house, I saw the needle getting very close to the red zone and I was worried that I was going to overheat before I made it there. To my great relief, I felt the fan kick on and my temperature dropped to a happy comfortable place.

With Nolimitz, we drained the old coolant, filled it up with water from a hose, and did a good rinse. Put the plug back in, dumped in some radiator flush, topped it off, and then ran the bike for a good 15 minutes. Then we dumped that and gave the rad a very thorough rinsing to get all the flush fluid out. Topped her back off with traditional Prestone coolant.

I rode the bike home and much to my delight, my temps remained stable and I noticed that the fan was reliably kicking on. I intentionally took a "stop and go" traffic route on the way home. Problem seems to be resolved.

One thing I noticed is that this bike's radiator cap is super old, and it appears to be rated for 13-14 PSI. Reading the forums here, I've learned that the 650 is supposed to have a cap rated for 7 psi. I ordered a Stant 10228 radiator cap from Amazon for 6 bucks and it'll be here today. I'll be curious to see if having a radiator cap with the correct pressure rating will have an impact.
 

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...One thing I noticed is that this bike's radiator cap is super old, and it appears to be rated for 13-14 PSI. Reading the forums here, I've learned that the 650 is supposed to have a cap rated for 7 psi. I ordered a Stant 10228 radiator cap from Amazon for 6 bucks and it'll be here today. I'll be curious to see if having a radiator cap with the correct pressure rating will have an impact.
If you look at Partzilla, for example, the radiator cap is the same across all the cx/gl range. With a 7 psi cap coolant will flow to the recovery tank at a lower temperature.
 

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'84 CX650E that is evolving into a GL500
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My 650 came with a 0.9 atmosphere (13 PSI) rad cap, which is the same as the GL500, GL1000 and GL1100 I've had and probably every other liquid cooled Honda of that era (not to mention most cars & light trucks until they started using the smaller size in the '90s). I've never seen anything to indicate that they should have anything else and I've always used 13 PSI caps.

I was about to say that I doubted you'd found something that says they should have a 7 PSI rad cap and that more likely someone mentioned using a 0.7atmosphere (10PSI) cap for some special application. I was about to click Post when I decided to search the forum for 7 PSI and see if I could find that too. I found one thread where someone gave incorrect information and another where someone quoted that misinformation. I verified that the iart number Honda specifies for the GL650 is indeed a 0.9 atmosphere cap and posted corrections in both of those threads.
 

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Discussion Starter · #32 · (Edited)
See, this is why I love this forum. I have sourced a proper 13 PSI cap at my local Oreilly's Auto Parts - the brand name is Murray and it's Part #7013. I'll plan on picking it up today. Thank you for setting me straight!

BTW, Bob, I LOVE that you posted corrections in those threads for anyone who may stumble into them in the future. You guys are awesome.
 

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Discussion Starter · #35 ·
Yeah, we drained the reserve tank and got things really well cleaned/rinsed out. My guess is that the coolant was ancient, and the electric fan had been out of use for so long that it needed some coaxing to get the cobwebs out. This bike had been sitting a LONG TIME before I took possession of it and began bringing her back to life. She's a BEAST now, though!
 

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Footnote:
After the above problem was sorted I did remember a circumstance where a full radiator with new coolant can cause overheating.

While my dad worked for BP's technical services division he also was assigned to represent the company at the 2 local race courses. So that meant free entry to races of any sort , too bad I was still at school and not have a motorcycle by then (1970's).
A couple of sponsored local race teams (privateers) were experiencing problems with overheating engines. We're talking 5 litre V8's by the way. At the same time other identical cars running the identical oils and coolant were going fine. The engines, radiators, water pumps, everything was identical. All the teams were provided with neat (not premix) anti-freeze anti-boil to mix when wanted. Nothing was leaking , , just some got extremely hot !
Then one of the affected cars mechanics commented something to the effect that BP's coolant was no good as he'd even put 100% anti freeze in and it still didn't work ..... it must be crap !

The problem is 100% anti-freeze --- glycol ---- is very viscous. Much thicker than water. Neat anti-freeze must be mixed with water (preferably distilled water) at 50/50 amounts maximum. The water pumps were not able to pump the stuff around the engine fast enough. It seems crazy but it's real.
From memory one team later opened up a water pump to find wear in the area around the impeller. Parts were not touching but it was like it had something in it polishing away the insides.

The moral of the story is read the product directions and more is not necessarily better.
 

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Footnote:
After the above problem was sorted I did remember a circumstance where a full radiator with new coolant can cause overheating.

While my dad worked for BP's technical services division he also was assigned to represent the company at the 2 local race courses. So that meant free entry to races of any sort , too bad I was still at school and not have a motorcycle by then (1970's).
A couple of sponsored local race teams (privateers) were experiencing problems with overheating engines. We're talking 5 litre V8's by the way. At the same time other identical cars running the identical oils and coolant were going fine. The engines, radiators, water pumps, everything was identical. All the teams were provided with neat (not premix) anti-freeze anti-boil to mix when wanted. Nothing was leaking , , just some got extremely hot !
Then one of the affected cars mechanics commented something to the effect that BP's coolant was no good as he'd even put 100% anti freeze in and it still didn't work ..... it must be crap !

The problem is 100% anti-freeze --- glycol ---- is very viscous. Much thicker than water. Neat anti-freeze must be mixed with water (preferably distilled water) at 50/50 amounts maximum. The water pumps were not able to pump the stuff around the engine fast enough. It seems crazy but it's real.
From memory one team later opened up a water pump to find wear in the area around the impeller. Parts were not touching but it was like it had something in it polishing away the insides.

The moral of the story is read the product directions and more is not necessarily better.
And worth noting some coolants and antifreeze are just that...
and same with inhibitors...need to check the specs...easy in internet days...
Interestingly running pure Ethylene glycol has a 15%to 30%lower heat transfer c/w a 50/50mix despite the higher boiling point...:)
 
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