Engine temp oscillating on gen2

[Julli]

I have a 2009 gen2 and it has some abnormal behaviour with engine temperature.
During steady speed driving engine temperature oscillates. First it reaches the normal temperature (just below the line about halfway on the gauge) and then drops down to about halfway between normal and cold engine.
This repeats basically all the time with a cycle time of 2...3 minutes.

So far I have replaced thermostat but it did not have any effect.
Also made the air hole on the thermostat larger from 2,0 mm -> 4,0 mm. This stopped oscillation but temperature did not reach normal level when it was colder. So I went back to 2,0 mm hole.
Has anybody had similar problems?

In Finland this seems to be relatively common issue but according Suzuki Finland this is only a feature and not a problem. Still it bothers me.

 

[BA BUSA]

Sounds like you might have air in the system...did you "burp" it to get all of the air out ???
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[jellyrug]

That's perfecty normal when riding cold weather.
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[Julli]

I am confident that there is no air in the system. Another thing confirming this is that this phenomenon happened also when the bike was almost new and cooling system had never been opened.

Of course this is somewhat normal when riding in cold weather but it happens also when weather is relatively warm like 25 celsius.