Didnt notice the thread at first, not a 500 guy really, so sorry for my late chime in..
I had a friend when I raced yz80s that I rode with in the desert, he owned an 87(or 86, I forget now) yz490, he used to do the leaning the bike thing, and then he found that before taking the bike off the stand he would open the throttle to half, and cycle the engine about 5-10 times with the kick starter.. then give it one good kick and it would usually fire up.
It was an air-cooled motor and a much differant/older open-class bike, but I thought it may be helpful info to try out. :cool:
edit:
Be careful with the kickstand if you go that route, not only riding with it, but even leaning on it to start the bike can be dangerous, it would be alot more stable on a stand. I took my kickstand off my bikes in the past because they could flop to the downward position and cause a crash.