Freedom Fighter Barry

I just a 1982 Yamaha XJ550 Maxim a few days ago. I am having trouble starting it when it has just been running maybe 10 minutes ago and is still hot. When I try to restart it, it just keeps turning over. Opening the throttle seems to help after a few seconds, but that's still too hard on the battery. After I do get it started, I have to use the choke for a minute, even though the bike is still hot. Help please? I put a brand new battery in it. It starts up perfectly in the morning when it's cool. I am in Wisconsin. It has not gotten cooler than 60 degrees or hotter than 85 degrees here since I got the bike and noticed this problem. Thanks!