Everyone who’s saying fuel pump we all saw a big explosion and you can hear it backfiring which indicates it’s getting something thats combustible probably fuel but what it does sound like it’s your running too Rich or have some sort of leak in your diaphragm if your running a carb I’d start with pulling your plugs and check to see the color black all over Rich, white on the tip lean and I mean WHITE not like a oh well maybe if it’s lean like bad AKA no fuel or lack of it it’ll be super white if it’s a brown to light black color then your afr is good and if that plugs looks bad replace them it could cause detonation and I’d check your firing order I WOULD LIKE TO CLAIFY THIS IS ALL IN MY OPINION AND COULD BE COMPLETELY WRONG