J2, oil expands like 10-12% from cold to hot -- that explains your window change. I always check mine cold for that very reason.
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This topic generated an "oil window war" because of a newbie's innocent question.
The points raised are fairly interesting and
you folks are the expert witnesses because you have the first hand knowledge that some of these debaters lack.
Have fun (assuming the war is still going on when you get here)
The very first Oil Window Level Warhttp://suzukisavage.com/cgi-bin/YaBB.pl?num=1288398790 
and here is the subsequent
Oil Change Method War that came from that one.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1289178835enjoy !!
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WARNING NOTICE !!Out of the window war and related side wars has come an
important hot test to perform on your particular bike after you have picked your side stand oil in the window level.
The hot test is simple and only has to be done once, after picking your handlebar alignment and resting condition, put your oil level stone cold where you want it to be for easy side stand walk up visibility. Then perform the hot test to assure yourself that this side stand oil level is completely safe after your oil is all hot and expanded.
The hot test:ON A LEVEL SURFACE crank your
fresh hot from a ride bike up, get it to a good idling rate (at least 1,000 rpm) and get somebody else to hold it straight upright while you shine a flashlight into the oil window with the bike running at idle.
Ideally, you would like to see an empty window --
but many do not.
If you see more than half a sight glass on this hot run test, then you need to take out some oil !!
You know the window empties completely when you crank it cold, cause you have already done this test with the bike stone cold. What has changed is that your oil went from garage cold to engine hot -- oil expands when hot to the formula 0.0004 / degree F, so for a 250-300 degree F delta-T you get like a 10-12.0% change in volume.
10-12% is a significant enough change in oil volume for you to do the check again when the engine is full from hard running hot.
On my bike I get just under half a window held upright when hot idling when I set the oil level to half a window on the sidestand with everything stone cold. I am lucky, what I see stone cold on the side stand is just about what I see on the hot held vertical test. You likely are not that lucky .....
You can't ASSume this hot check oil level works out this way for you, your garage isn't at the same degree of level as mine (mine isn't perfectly level) and my side stand is slightly bent and I use a sidestand adder magnet on the foot of my side stand and my oil expands like RotSyn expands (your oil likely expands slightly differently).
You have to check your own situation to find out what your hot expansion truth really is.
UNDER NO CIRCUMSTANCES should you see a full oil window when idling a fully hot engine held bolt upright. This would put you in danger of splashing oil with your crankshaft. You need a half window or more of oil clearance to the crank splash shelf with your worst cast oil expansion due to hot engine temperatures -- a full window of clearance is of course the "optimum desired" amount of clearance but
many do not get this optimum level on the hot test due to oil expansion.
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