I had a 2000 Katana 600 that had a similar problem. Sometimes it would start and sometimes not. I figured out that I had to do a certain "routine" to get it running. First sit on it and retract the kickstand, then hold in the clutch, flip the kill switch to run, then press the go button. If I flipped the kill switch to run then held in the clutch, I got nowhere. Don't know why, but that what I did with my bike. Maybe yours had a funky personality like mine did.