57 the screw member 57 bracket 56 and stop member 55 may be vertically adjusted to the precise vertical position for the stop member 55 to engage the top of each of the needle bars 47 and 48 at the upper limit of its stroke accordingly when the adjustable pivot pin 28 in the elongated link bar 27 is released and moved along the slot 29 of the bell crank 31 in order to adjust the length of the vertical stroke of the push rod 18 and thereby the needle drive member 17 the stop member 55 may be vertically adjusted to accommodate the upper limit of the stroke of the needle bars 47 and 48 corresponding to the stroke of the drive member 17 both the adjustment of the stroke of the push rods 18 and the position of the stop member 55 may be executed with a minimum of delay and effort fixed to the machine frame 11 is a spring member 60 extending forward and being looped around and through a notch 61 in the upper end portion of each of the needle bars 47 and 48 the spring member 60 is biased to urge the corresponding needle bar 47 or 48 into its upward position toward and against the stop ledge 55 when that particular needle bar has been unlatched by retraction of the respective latch pin 38 thus when the needle bar 47 or 48 is disengaged in its inoperative position it remains stationary in its elevated position while the drive member 17 continues to reciprocate carrying with.