The safety features on your machine shut down the engine when you don't follow procedures. When the engine shuts down under these conditions, as the RPM drops down, the throttle governor opens the carb throttle more in an attempt to maintain RPM. When this happens, unburned fuel passes thru the engine and into a very hot muffler where the temp is hot enough to flash the fuel causing this loud bang.
Years ago I was mowing lawns for a friend in the lawn care business who had injured himself. He asked me if I could do some of his customers lawns while he was healing and I said yes. I had finished mowing one of his customers, put my mower in my trailer, but shut it down too soon and it did the "gunshot" bang thing. As I was cleaning up this driveway with my blower, the local police came screaming up to the house, ordered me to the ground!!! The next door lady had called the police saying that she heard gun shots!!! The police took me away in cuffs, searched for the gun in my trailer, truck, the nearby sewer drain, it wasn't very funny for a while. I told them it was my hot tractor that I had shut down too soon, but they still did a gunpowder check of me and my equipment after impounding my truck, trailer, and equipment. It cost me lots of grief and time, and the town sent me a bill for $3,500 for the cost of the investigation!!! I ended up in court, didn't pay the town anything, but had to pay the court costs.
My friend thought it was hilarious, but it took me a long while to get to that point!!!!!
I did some research in local newspaper archives and found that this lady had made many calls to the police over the years for dumb reasons. I sent the police chief a request for a fireworks permit with her address on it, well, I thought it was funny, after all, they (three officers) came after me with weapons drawn and all I had was a leaf blower and hearing protection!!!! Good thing my leaf blower didn't bang when I shut it down, they would have shot me!!!!!
Mad Mackie in CT:biggrin::laughing: