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Discussion Starter · #1 ·
Got the bike out of storage yesterday, changed oil and went for a ride to work things through. As I was riding, noticed the temperature gauge rising from 178 to 196 and then back down...over and over again. Historically the temp has hung between 178 on cool days and 186 or so on hot days. Any ideas why this may be occurring? Oil level is good, going to check coolant today as bike was too hot yesterday but it just doesn't seem logical to me that it would be coolant level. Is there a thermostat or sensor (I know stupid question, of course there is) that may be the real culprit, is it the dry gas I need to burn through?...any input would be incredibly worthwhile. Peace.
 

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Discussion Starter · #6 ·
I guess the question begs to be asked....why is this occurring now when previously it held the temp steady (minor fluctuations of course but **** near consistent)? This temp change is happening pretty quickly, like a degree up every couple of seconds until it maxes at 196 , then down the same, then up, then down repeat infinitely, ad nauseum.
 

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I have the same problem with My 03 sv, NORMAL thermostats do not fluxuate that way.
I plan to change my thermostat as soon as I get time. I have never heard that a temp reading fluxuating more than 10 degrees on any thermostat cooled engine I would know I am a Dynamometer engine tester.

GO ARMY
 

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Is this while you are riding at speed?

I only notice this while stopped and no air is getting to the radiator, the temp will jump a bit , once I get moving it settles around 185 or so.
 

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The service manual for my 1000 says 88 *C (190 *F). Dunno if the 650 uses a different thermostat...
good point, I have the 650 service manual here, it says the thermostat should switch OFF->ON at 208°F, ON->OFF at 198°F. so I was running a little hot.

and if the OP's issue is related to the thermostat, it's faulty.
 

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Two cents worth of advice on temp variations. If you're riding and see temps consistently above 210f, your thermostat is running wide open and your fan is no help above 20-30 mph.

Drop down a gear and slow down to the same RPM as before and see if you don't get a drop in temp. Don't wait for the light to come on!
 

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The purpose of the thermostat is to keep the engine at operating temperature. So yes "engine cool thermostat closed engine warm thermostat open", but the thermostat is NOT supposed to open and close for a period of time once a fully functional and operational thermostat opens it has no need to close because the engine temp should remain the same. "Normal operating temp" Now that is so much simpler.:nana:
 

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I guess the question begs to be asked....why is this occurring now when previously it held the temp steady...
Good question.

I believe your thermostat is sticking. Instead of smoothly fluctuating tightly around the 190 deg design range, it fails to open until say, 196 deg (too hot), where it pops open all at once. Once open, it fails to close until it 178 deg (too cold). Cycle repeats, too hot, too cold ...

You can test if this is really your problem by following the steps in the Factory Service Manual, or just replace the thermostat.
 

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Thats exactly why I said I plan to change it. ...
Agreed. Rapid fluctuation over a 20 deg range means something is wrong. smiley

If the thermostat were stuck closed you'd be in trouble once the bike warmed up!
 
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