I have a 2008 gsxr1000 that I bought brand new. It only has 4500 miles on it. It sat in a garage for about 2 years then without draining old fuel (only had about 1/4 tank) I topped it off and rode it to my brothers about 30 miles where it sat for another year. I went to get it to bring it to my house. I had a hard time keeping it running without holding the throttle. Took off down the road with my wife following. It was sputtering for the first mile or so then ran a little better. A couple minutes in I hear my wife honking and motioning for me to pull over. There was a fire on top of the exhaust almost directly below the rear shock. It’s now been another 2 years since that happened and I just started working on it. Drained the old gas, got the rear caliper unstuck. Need to get a battery but I don’t know what caused the fire. My best guess is fuel but where did it come from? Also what else should I do before I try to start it? Any help will be much appreciated.