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Discussion Starter #1
On my bike I've installed an aftermarket digital temperature gauge, with the awesome advice from another forum member littlebr4d. I also replaced the thermostat because it was defective, flushed the radiator and refilled with coolant.

Today I went out riding to practice proper stopping, turning and motorcycle basics as I am a newbie and want to make sure I'm safe before going out with real traffic....

As I was driving around on 1st and 2nd gear, I noticed that the bike would increase temperature. It was averaging about 210 to 215 F and I got as high as up to 233 F. On this digital gauge the warning light turns on at 210 I believe... Today's temperature here in Winnipeg (Canada) was 27 degrees Celsius which is equal to 80 degrees Fahrenheit.

A couple things I observed:
- on 3rd and 4th gear, the temp would be about 210 F and the warning light would turn off
- I have a leak at the bottom rad hose on the left side of the bike, which I am hoping is why the bike is getting warm so quickly

So with all this happening, does anyone know what is the normal operating temperature of the CX500's? The stock temp gauge just has white and red lines and no actual values. Ive read another post that states the thermostat fully opens between 199 and 205 F but this only partly answers my question.

My bike is a 1979 CX500 Deluxe. 2-2 no h-box with pods and properly jetted. Idles at 1100.


*Note* in my attachment it looks like it says 5 but it's actually 215. The camera on my phone didnt jive well with the gauge display lol..
 

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It's been so long since I rode a CX with a digital temp gauge that I forget what the normal readings are... I probably wrote them down somewhere.

As a point of reference, though, the thermostat on these bikes does not fully open until 95C (203F). Starts to open around 180F.
 

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One other thing... what is the expected Ohm range for the temp gauge? Did you use the stock sender or one supplied with the gauge?

The Honda sender registers ~20.3 Ohms at 230F in theory.

I have seen some aftermarket gauges give weird readings when hooked up to the stock sender due to expecting a different range.
 

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Discussion Starter #7
Maybe you need to check whether your new instrument is lying to you with an infrared heat gun.

They make a great reality check.
I will try that out. Going to also fix my leak to see if that helps a bit. I could also do the e fan conversion but my mechanical fan is in surprisingly great condition.

Hopefully someone has an answer to my temp question 🤷‍♂️
 

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Discussion Starter #8 (Edited)
One other thing... what is the expected Ohm range for the temp gauge? Did you use the stock sender or one supplied with the gauge?

The Honda sender registers ~20.3 Ohms at 230F in theory.
This is the gauge:

http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=251582282565&category=33682&pm=1&ds=0&t=1508838282000&ver=0&oversion=b1a9e8b6

And this is the adapter

https://www.ebay.com/itm/1-8-27-NPT-Female-to-M16-x-P1-5-Gauge-Sensor-Sender-Thread-Adapter-Reducer-/371132988606

Attached is a screenshot of the old one (blue) vs new one (red).

Unfortunately the specs on the new gauge don't mention anything about ohms:

Description :
2" 52mm DIGITAL BLUE LED WATER TEMP GAUGE W. WARNING LIGHT

This series is fully electronic with a red digital LED readout, which allows for easy viewing at all angles during any lighting conditions.

Instructions:
* 6 Months Warranty
* Size:2 inch gauge or 52 mm diameter
* Power: 12V / MAX 0.3A
* Unit: F
* Color: BLACK
* Read: 104-300 F
* Style :Red Digital Readout


Includes:

* 1 X Water Temp Gauge
* 1 X Sensor


On a side note, at some point id like to collect all the data I can and make a build thread for others who want to do the same type of mod.
 

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Oh boy. That is a class-3 leak. Fix the leak 1st. Then re-fill with the motor cold from the radiator cap, don't depend on the reservoir bottle to refill. Air comes in as A-Freeze leaks out, or as the motor cools,
and only causes more overheating issues.
As best as I can tell from the video, it looks like your clamp is too big, or too loose, or both.
Optimal coolant temp. for most cars and water-cooled motorcycles is 220-230 F in a closed, pressurized system.
A leak compromises the pressure, reduces the amount of coolant, and allows air into the system, any or all of which can lead to overheating.
 

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When I had this gauge fitted I regularly checked it against my IR temp gun
on the heads and plumbing.
My thing ran at around 90C fully warmed up and would only ever approach 100C in heavy stop/go traffic
until the fan kicked in.

 

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Discussion Starter #14 (Edited)
UPDATE:

Took the bike out today to check if I fixed the leak and also monitor the temperature on the gauge. Weather was 23C / 73 F in the late evening with sun going down.

I was primarily on first and second practicing proper braking and didn't go higher than third gear.

As I rode, bike temp seemed to average between 203 and 215 F' with the lower temp when I was on third gear (I now understand the purpose behind the e can conversion and how it cools the bike).

At the end of my ride, I parked, and saw that the temp gauge was up to as high as 262.

- No coolant leaks anywhere. Fixed.
- Saw a tiny bit of smoke from the front and it smelt a little like crispy toast but nothing that seemed alarming.
- Oil level was a bit lower than when I had did the oil change 2 months ago. Refilled that.

As per recommendations from other members, my next step is to check the temp with an IR gun.

https://youtu.be/7EK9ZzsPrS0
 

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I understand you driving in 1st and 2nd while practising braking but how did you get to the place where you practised without using at least 4th gear? Even with the extra weight of the sidecar I generally use 4th or 5th at 50 Km/h...
 

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Not much of the probe with the adapter would be in the water flow like the original. The original would be in the full flow of water.
 

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Discussion Starter #17
I understand you driving in 1st and 2nd while practising braking but how did you get to the place where you practised without using at least 4th gear? Even with the extra weight of the sidecar I generally use 4th or 5th at 50 Km/h...
I got into 3rd or 4th when riding along really long streets where I could practice staying in those gears. With that being said, i didn't spend much time in those gears .
 

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Discussion Starter #18
Not much of the probe with the adapter would be in the water flow like the original. The original would be in the full flow of water.

Thanks for pointing that out. Attached is what it looks like with the probe in. You can see that it doesnt go as deep as the original.

Are you thinking this could be a big contributor to an inaccurate reading?

Any suggestions how I can extend it?
 

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I understand you driving in 1st and 2nd while practising braking but how did you get to the place where you practised without using at least 4th gear? Even with the extra weight of the sidecar I generally use 4th or 5th at 50 Km/h...
I'm barely in 3rd at 50km or 32mph?
 

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It would be my guess that the temperature sensor in the adapter will give just as good an indication of temperature as the original. You can check with an IR temperature gun for peace of mind.
 
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