Hmm... If the temp is always stable with the engine off then it may not be electrical unless you've got a problem with voltage regulation or there's noise somehow being transmitted to the ECU or sensor wires. On the radiator side of things any air in the system should be nearly saturated (relative humidity close to 100%) so it would have basically no evaporative cooling effect. It almost sounds like your coolant is surging, where the flow is changing rapidly and your engine is getting hot and cold slugs of water. I assume you've verified your cooling system is full? Does the temp fluctuation seem the same when the bike is first warming up, before the thermostat opens?

If the sensor is easy to get to and you can plug the opening, I'd pull the sensor out (you may need to ground it) and put the wet end in a cup of hot water. Run the engine and watch the temp. If the up and down fluctuation stops then either the sensor is affected by engine vibration and should be replaced, or there's something up with your cooling system.

 

as stated before, it is a simple ground wire. you have looked for everything but this so i dont care if you fix it or not.

how do i know? i had the same fukn problem.

 

In the context of your lecture about not fixing things yourself, what you stated before sounded like nothing but an off the cuff remark by someone who doesn't know how to troubleshoot problems. I don't put a lot of stock in replies like that. I would have given your comments a lot more consideration had you given us the whole story.

So where exactly is this simple ground wire? There are lots of "ground" wires, some are true grounds and others are simply signal negatives that aren't actually grounded at all. What did you actually see and hear first hand when you learned of this ground wire issue?

 

I was really busy the last couple of weeks .but what I did, I fallowed SD2007
And I took off the sensor but I haven’t put it in hot water yet. But I ll keep you stated.
Thanks man, really appreciate your help.

 

Given Tbagr's most recent post it sounds more likely to be a problem on the electrical side.
Since you've already removed the sensor, go ahead and try the test I described if it's not too much of a pain. If the fluctuation is still there when the engine is running, then I guess grounding is next. The trouble is that doesn't narrow it down very far, but at least it's something.