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Discussion Starter · #1 ·
This evening was my second ride on the bike and it was hot. The air temp was around 94 degrees and I was riding two up. During the first ride on Saturday it wasn't as hot and I rode single and had no overheating issues. Saturday was cooler around 85 to 88. Once the bike warmed up this evening it stayed all the way to the right on the H. We rode from 25 to 55 at under 5k rpm. The ride lasted about 45 minutes and when I got home a little of the coolant leaked under the bike from the overflow tank. Although the bike has only 3100 miles it still has a 31 year old thermostat. I replaced the original radiator temporarily until I have it welded (long story my FUBAR). When I had the radiator off, I cleaned the fan but it would not turn which I though odd. So, if you were me where would you start?
 

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A cx500 fan will not turn. But a gl500 and gl650 will turn because they are electric fans.



Maybe do a radiator flush with vinegar. Aboout two quartz. Run it for a good time. Let it set over night or some let it sit two nights then flush with plenty of fresh water. Mix up a 50/50 antifreeze/coolant. You do have antifreeze/coolant mix in it right now? Otherwise you will run hot.



While the engine is cool remove the radiator cap and start the bike. Watch the water see if it gets hot and circulating.



Also when was the last time you changed the oil.



Make sure both are up to there proper levels.



If the oil hasn't been changed and the bike has just water in the cooling system that will cause a bike to run hot. Really hot if either or both of the levels are low.



Don't leave it this way for to long.
 

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Discussion Starter · #3 ·
A cx500 fan will not turn. But a gl500 and gl650 will turn because they are electric fans.



Maybe do a radiator flush with vinegar. Aboout two quartz. Run it for a good time. Let it set over night or some let it sit two nights then flush with plenty of fresh water. Mix up a 50/50 antifreeze/coolant. You do have antifreeze/coolant mix in it right now? Otherwise you will run hot.



While the engine is cool remove the radiator cap and start the bike. Watch the water see if it gets hot and circulating.



Also when was the last time you changed the oil.



Make sure both are up to there proper levels.



If the oil hasn't been changed and the bike has just water in the cooling system that will cause a bike to run hot. Really hot if either or both of the levels are low.



Don't leave it this way for to long.
I have new oil and 50/50 coolant that is new also. The radiator looked ok but I think I will drain it and run the vinegar through it. What about the thermostat?
 

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It could be the thermostat, Bob. Did you feel if the chrome transfer pipe was hot when you were having problems. When the thermostat opens, the coolant starts to flow thru it. I assume your fan is firmly attached? On one of my bikes, the fan nut backed out and the fan slipped off the camshaft. It was just sitting there behind the radiator.



It certainly won't hurt anything to vinegar your system, but I think there is more to it than that.
 

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Discussion Starter · #5 ·
It could be the thermostat, Bob. Did you feel if the chrome transfer pipe was hot when you were having problems. When the thermostat opens, the coolant starts to flow thru it. I assume your fan is firmly attached? On one of my bikes, the fan nut backed out and the fan slipped off the camshaft. It was just sitting there behind the radiator.



It certainly won't hurt anything to vinegar your system, but I think there is more to it than that.
I am going to have it inspected this morning. I will check the chrome pipe to see if it is hot. I am pretty sure the fan was attached tight. It could very well be the thermostat. I will update this when I get back.
 

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Discussion Starter · #6 ·
I just got back from having it inspected and in the 10 minutes it was running the temp gauge was almost in the red.It is 95 and high humidity so that plays a role but I have no idea why it is running so hot. I checked the chrome pipe and it was very hot to the touch. The bike was fine after getting it running but since that first ride she is a hot one. Thermostat?
 

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Thermostat?

Possibly and its an easy thing to check by testing or fitting another



Dont try and turn the fan/engine with a spanner or socket BTW !!!

Bad idea, they dont like it.

Use a 17mm socket on the front of the crankshaft
 

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If your needle is running to the right of the H, I would strongly recommend not running it until you diagnose the issue.



The coolant pipe will be hot to the touch, it has 180 degree coolant running through it.



First order of diagnosis would, IMO, be to check function of the 7v regulator.
 

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Discussion Starter · #9 ·
If your needle is running to the right of the H, I would strongly recommend not running it until you diagnose the issue.



The coolant pipe will be hot to the touch, it has 180 degree coolant running through it.



First order of diagnosis would, IMO, be to check function of the 7v regulator.
I am ok at most stuff but electrics are a weakness. What is the 7v regulator and how would that affect the bike running hot? I really appreciate the replies!
 

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I am ok at most stuff but electrics are a weakness. What is the 7v regulator and how would that affect the bike running hot? I really appreciate the replies!




The temperature guage runs off a 7v line, from a regulator that is a small black box behind the speedo on most of our bikes. If it fails, your guage will get sent too much voltage, and off the scale she goes.



You need to track the box down, and use a multimeter on it to determine what voltage it is sending to the guage.



When you have ran hot, have you heard any bubling/boiling at the top of the engine upon shut down? If not, I'd suspect you are not likely hot at all. I had a fan fail on my old 500, and the guage climbed real close to the edge and I could easily hear it.
 

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Discussion Starter · #11 ·
The temperature guage runs off a 7v line, from a regulator that is a small black box behind the speedo on most of our bikes. If it fails, your guage will get sent too much voltage, and off the scale she goes.



You need to track the box down, and use a multimeter on it to determine what voltage it is sending to the guage.



When you have ran hot, have you heard any bubling/boiling at the top of the engine upon shut down? If not, I'd suspect you are not likely hot at all. I had a fan fail on my old 500, and the guage climbed real close to the edge and I could easily hear it.
At shutdown, I can hear the coolant bubbling and and it spits up a bit of coolant on the ground. I will check the regulator and see what is happening there next. I am at a loss other than it is hotter than HE double hockey sticks right now.
 

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The 7 volt regular feeds the temperature gauge with a constant 7 volts. If you didn't have one, the voltage in the bike can range from 12 or so volts, to 14.5. This would make the temperature gauge inaccurate as it depends on voltage as a reference.



They are at different spots on different bikes. May be clipped inside a rubber cover on the back of the tach or speedo. I have also seen them inside the headlight bucket too. It is a black cube about 3/4" on the sides with 3 wires extending from it. I'm sorry, don't remember the colors, think yellow, green and black.



You can measure the output on the yellow wire to ground. Should be 7 volts. If I am telling him wrong, guys, speak up. It has been awhile since I messed with one. They can be built from Radio Shack parts that cost only a couple of bucks. I think the details may be on the Quick Reference post. I know Shep has the plans on his site too.



Is there also a possibility that the impeller nut came off and the impeller isn't spinning? That can happen. You did check the coolant level at the radiator, not the overflow bottle didn't you? The overflow bottle isn't a good indicator of coolant level.



Let us know what you find.
 

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Clean out radiator with vinegar and water as described earlier.



Replace your coolant/ water combination with Engine Ice and 3 ounces of Water Wetter.

Well, for that matter, you could just add 3 ounces of water wetter to the coolant that you already have. It's compatible with all coolants.



If the bike does not run cooler after that, you need to check a couple of things:



1) Carburetors. One of the two sides (or both) may be running lean. You can usually determine this if one side of the engine is hotter than the other, especially the exhaust downpipes.



2) Camshaft broken at the water pump. Rare, but happens. You have probably ruled this one out though, if the chrome pipe got heated quickly after the thermo opened, your pump is good.



2) Main bearings. No way to check this easily if it is just starting to go. If they are readily on their way out, you will find brass in your oil.
 

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Avatar looks like a 78 maggot, IIRC the regulator was in the headlight bucket, thanks Blue.



Good thoughts also about ensuring the impeller is turning.
 

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Discussion Starter · #16 ·
looks like more work ahead for me. And I just got it plated today. Darn the luck. By the way, what is a 78 Maggot? It's a 79 base with a deluxe seat 3174 miles.
 

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Discussion Starter · #17 ·
Well, I worked on the cooling system and the fan is turning just fine. She is still running hot though. I have Engine Ice to put in but I think it has to be the thermostat. I will soak it in vinegar until my thermostat gets here. If that does not fix it I will be at a real loss.
 

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I was going to mention on my last post that the early to mid 80's thermostat for a Honda Civic is a direct replacement for the ones in our bikes. But if you have one coming, you may need to take it.



You could also try spraying a light mist of cool water from a hose on the front of the radiator and see if that lowers the temp any. You may have some blocked tubes in there that are not allowing coolant thru.
 

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A cx500 fan will not turn. But a gl500 and gl650 will turn because they are electric fans.



Maybe do a radiator flush with vinegar. Aboout two quartz. Run it for a good time. Let it set over night or some let it sit two nights then flush with plenty of fresh water. Mix up a 50/50 antifreeze/coolant. You do have antifreeze/coolant mix in it right now? Otherwise you will run hot.



While the engine is cool remove the radiator cap and start the bike. Watch the water see if it gets hot and circulating.



Also when was the last time you changed the oil.



Make sure both are up to there proper levels.



If the oil hasn't been changed and the bike has just water in the cooling system that will cause a bike to run hot. Really hot if either or both of the levels are low.



Don't leave it this way for to long.


GL500s do not have an electric fan.
 

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Well, I worked on the cooling system and the fan is turning just fine. She is still running hot though. I have Engine Ice to put in but I think it has to be the thermostat. I will soak it in vinegar until my thermostat gets here. If that does not fix it I will be at a real loss.


Engine Ice is a great coolant, but it's Water Wetter that really makes it (or any coolant) more efficient.

http://www.redlineoil.com/product.aspx?pid=74&pcid=10
 
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