What do you mean, "All the way up?" All 8 bars come on?? Your fans should kick on around 6-7 bars. I don't remember exactly as it happens so seldom on my '07.
If your getting more than 6 bars and the fans aren't on, that itself is an issue. If your going to full 8 bars, as said above, you prolly have a stuck thermostat. OR you have a bubble in there. Anyone change your coolant lately?
Also, your fans should not work when the bike is off.
Yes, when I am stopped at a long light it will climb up to all bars. When I get in my garage I put the kickstand down which kills the engine but doesn't shut off the bike. While just standing there the bike's fans are running.
Just to be clear, there are 10 bars on the temperature gauge of your GenII.
Normal running, which you seem to get, is 4 bars. To me, that suggests the thermostat is not stuck open or closed, and I doubt your temperature indication would remain constant at 4 bars during a range of "normal" running if the thermostat was stuck somewhere between. I can't conceive of a thermostat that only opens when it sees more water pressure from the water pump as the engine speed rises above idle.
If stuck at a "long" light, I'd expect your temperature gauge to climb 6-8 bars, somewhere around there the fans should start; once started they should bring the temperature back down within a few tens of seconds/very small number of minutes.
As garyhouse suggest, just start it, let it idle. Watch the temperature gauge, listen for the fans. They should kick in at the appropriate number of bars (I can't remember whether it's 6 or 7). From that point on the gauge should go down again; the fans will turn off at 4 or 5 bars, then the engine will heat up again. If the fans don't start, there is a problem with the fan circuit, if the fans run but the engine doesn't cool I'd suggest a blocked radiator or some such.
If ever the gauge goes to 9 or 10 bars, you do have a real problem.
I suppose it's possible there is some air in your cooling system that only allows water to circulate when the water pump pressure is high (normal running) but not when low (idle).