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Discussion Starter #1
I noticed that my CX550 C 1980 was running hot and discovered that the fan had become unscrewed. After reattaching it and with new Stant radiator cap, 50/50 water coolant solution, new sensor and new thermostat, on the freeway on a day in 70s (F), the needle goes to the middle of the thick line, which is not much better than before. Perhaps my memory fails me, but it seemed like before the temperature was quite stable, rarely moving from where the thin and thick lines meet. My guess is that the coolant is not circulating fast enough, and the only problem I can think of is that I replaced the stock rubber hoses with some with a slightly smaller inner diameter, but it doesn’t seem like this should make much difference in performance. Does anyone have any ideas of what might be the problem?
 

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Are you sure that the sensor is good and the correct one for the bike?
If you have access to an IR temperature gun take some readings with that to ensure that you do in fact have a heating problem and not just a new normal.
Check coolant level as well.
 

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Are you sure the thermostat is in the right way?
I did the cooling system upgrade a few months ago, so I don't exactly remember how I did it, but it didn't seem to be more than one way to put it. I can tell when the thermostat opens, or least I think I can, because I have seem the needle go down when it opens. I did a test by idling the engine for about an hour and kept an eye on the thermo needle. I suppose it would be worth a second look if there aren't any better suspects.
 

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Are you sure that the sensor is good and the correct one for the bike?
If you have access to an IR temperature gun take some readings with that to ensure that you do in fact have a heating problem and not just a new normal.
Check coolant level as well.
The fluid level are good. As for the sensor, I got it from ebay, but the part number matches, it fits, and appears to be in the original box. I could put the old one back in to see if there is any difference. I don't have an IR temperature gun and am learning toward this being the new normal. The ramifications of overheating are real to me, as I went several years wondering why my battery was always going dead. I finally figured out that my stator got burned out from one of the times of overheating and wasn't charging the battery. I've changed the stator and of course don't want to do that again. As long as the needle doesn't get too close to the red line, I guess I'm OK, just would prefer it stays as far away as possible. Thanks for your thoughts.
 

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Looked at the parts manual and it looks realy hard to put in the wrong way, thermostats do come in differant heat ranges , which would make it run hotter if you have a higher temp thermostat. Make sure the wire going to the sensor is not grounding out some where , and check voltages on the bike as to the guage and at your battery,and might be time to clean the grounds.
 

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Discussion Starter #7
The thermostat was a genuine Honda part, so unless it's defective, it should be operating at the proper temperature range. I will see about checking the possible electrical issues. I don't always understand what setting the voltage meter is supposed to be set on. BTW, noticed you are near Vancouver, BC. Have you ever considered a ride to Alaska?
 

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If I won the lottery or can get paid to ride, I'd go, plus every where else. Over thirty years since I rode the coast hwys to San Fransco. Job I have doesn't come with much time off.
 

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If I won the lottery or can get paid to ride, I'd go, plus every where else. Over thirty years since I rode the coast hwys to San Fransco. Job I have doesn't come with much time off.
Here is to hoping you win the lottery! Went to Alaska via Al-Can in a VW van in the late 70's. It was austere. The California coast is hard to beat - glad you made it when you did.
 
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