I have a 98 ZL 500 that will start and run for awhile, then start backfiring and dies. It just started doing this 2 days ago, before that it was running just fine. I have cleaned out the carbs and changed the plugs and it still does it. Also if it is running and you turn it off with any of the switches(ignition, kill switch, or tether) it won't shut off, it will just start running rough. Any ideas?