A gas engine with ignition will backfire, if you get it flooded or if there is a problem with the pick-up. I used to swear you never needed a glove with ignition, untill I got my fingers bent back hard from a bad sensor. A few months later, I flodded a 4.2 and it really mangeled a couple of fingers. I always hand start my motors, but I use a glove. I also always choke with throttle closed and switch on so it will pop before it floods.