In the Southern Hemisphere, where the June solstice is known as the shortest day of the year, it marks the first day of astronomical winter, but the middle of winter in meteorological terms.
Backfill refers to products or materials used to fill excavations. The most common form is composed of a mixture of gypsum and calcium bentonite. Apart from filling holes, one of the primary purposes is to mantle sacrificial anodes under the ground.
Real backfiring means the engine is not properly timed and the fuel/air mix is getting a spark and ignition at the wrong time (when the intake valve is open). Real backfiring is actually the bike spitting up in a sense, backwards through the carburetor or intake. So, the popping you are hearing is not back-firing. It is a popping resonating sound generated by a lean condition on deceleration. When you suddenly close the throttle, the incoming air is choked off and the closed throttle also causes the bike to return to idle on the very lean idle circuit.