In a cup sealing system including a cup former and at least one burner for sealing a cup bottom seam where a cup side wall blank is mated with a bottom disk, with one portion of the side wall extending beyond the bottom disk, an improvement wherein at least one burner includes a burner head with a plurality of circumferentially arranged flame nozzles and a pilot flame aperture, the pilot flame aperture adapted to be located axially adjacent the one portion of the cup side wall; a flame ignitor/sensor positioned adjacent the flame aperture; and a combustion chamber which extends from a forward edge of the burner at the flame nozzles to a location axially beyond the container side wall to thereby achieve uniform heating of the extended portion of the cup side wall. The burner head also includes a pair of relatively movable sleeves adapted to create an annular pilot flame ring gap on start-up.