Well, almost every time something like this happens, it's because of something you did. So, I'd recommend you raise the tank and remove the spark plugs one at a time. Make sure that there is no anti-sieze on the exposed end where the electrode is on each of them. Clean the threads so that there is only the smallest dab of anti-sieze on the threads. Check the wire carefully on each plug as you reinstall them. Then look at all of the wiring that you have to touch as you put things back together to make sure all connections are good. Look at the fuel lines and make sure they do not get pinched or folded as you lower the tank. Charge the battery fully. Then fire it up.