Temp. changes sporadic - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 16 (permalink) Old 04-28-2014, 03:45 PM Thread Starter
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Temp. changes sporadic

So, while riding I noticed the temp. suddenly dropped instantly from 78-83c to 68, then jumped back to 78. Later started dropping little at a time, then went back to staple 78-83c

Guessing a bad sensor, would anyone suggest differently before I go buy a new one?

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post #2 of 16 (permalink) Old 04-28-2014, 05:36 PM
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Are you SP1 or SP2?
I have an extra OEM SP1 sensor you can have...

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post #3 of 16 (permalink) Old 04-28-2014, 06:54 PM
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Or a bad or broken connection....



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post #4 of 16 (permalink) Old 04-29-2014, 01:04 PM Thread Starter
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Im SP1 - will have time to go through the connections tomorrow, but with a bad connection I would suspect the temp to disappear completely?

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post #5 of 16 (permalink) Old 04-29-2014, 10:03 PM
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Originally Posted by jondog9 View Post
Are you SP1 or SP2?
I have an extra OEM SP1 sensor you can have...
The sensor mounted on the thermostat housing is the same on both SP1 or 2 so any temp sensor would do.

Since this sensor is working based on variable resistance value caused by temp changes, Hanberg is right I believe. If any of it's 3 wires had a poor connection, the temp indication should be lost.
My guess is just a faulty sensor.

But still....one can never be too sure of anything when it comes to electrics.

Swap the sensor with one that you know it works and see what happens.


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post #6 of 16 (permalink) Old 04-29-2014, 10:15 PM
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Also,
You could pull your sensor, put it in a pot of water on the stove and check it's resistance as the water heats up.

I don't know what value is needed at what temperature but it may show a temp range were the ohms don't change or something.



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post #7 of 16 (permalink) Old 04-29-2014, 10:23 PM
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Also,
You could pull your sensor, put it in a pot of water on the stove and check it's resistance as the water heats up.

I don't know what value is needed at what temperature but it may show a temp range were the ohms don't change or something.



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Page 384 on the manual



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post #8 of 16 (permalink) Old 04-29-2014, 10:24 PM
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Page 384 on the manual

Thank you Sir, knew I read it somewhere.

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post #9 of 16 (permalink) Old 04-30-2014, 10:00 AM Thread Starter
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Crap, I thought it was the one in the radiator?

So, Im not that much into the function of the cooling system. I know my mechanic checked the thermostat when he had the bike for valve-check.

And I just pulled the left fairing, dried drops of coolant down the generator-cover, and the reservoir was pretty much empty. Filled to max and went for a ride, temp. stable around 77-78 while riding, and rose nicely to 103 when parked and dropped nicely when the fan came on. There were coolantspray again.
So I guess there is a leak somewhere, will have to check later

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Last edited by Hanberg; 04-30-2014 at 12:09 PM.
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post #10 of 16 (permalink) Old 04-30-2014, 04:46 PM
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Crap, I thought it was the one in the radiator?

So, Im not that much into the function of the cooling system. I know my mechanic checked the thermostat when he had the bike for valve-check.

And I just pulled the left fairing, dried drops of coolant down the generator-cover, and the reservoir was pretty much empty. Filled to max and went for a ride, temp. stable around 77-78 while riding, and rose nicely to 103 when parked and dropped nicely when the fan came on. There were coolantspray again.
So I guess there is a leak somewhere, will have to check later
SP1's use the more simple thermal switch mounted into the left radiator to switch on the single fan, while the SP2 uses a sensor mounted into the thermostat housing which sends a signal to the ECU to switch on the dual-fans via the fan control relay.

Your leak could be from a loose hose clamp, or a possible crack in the left radiator.
I've heard comments from SP1 owners where the radiators are prone to develop cracks due to only two mounting bolts vs. three on the SP2.
Check near the mounting tabs if there is coolant residue nearby.

I had a similar leak problem with my SP2 due to a puncture in the upper radiator tank by the prior owner, who repaired the puncture with JB Weld.
That repair didn't hold due to the radiator flexing with each heating/cooling cycle, and I found coolant dripping down my radiator and onto the ground.
Was able to have the puncture welded and pressure tested.
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