may be the globe plug needle gate or ball type or the like in a simple one way construction or may be 2 or 3 way as desired to attach to the motorcycle system a tee 50 is utilized in the preferred embodiment attached to the valve 48 for conveniently positioning the auxillary tank system to main motorcycle carburator feed the tee 50 may be of the compression flare type or the like with barbed style being preferred the tank 20 is mounted to the motorcycle with a pair of undercarriage arms 52 these arms 52 are planar with the underside of the tank bottom 22 and attached either directly by fusion welding or bonding as shown in fig7 or may have an arm attaching base 54 connected directly to the tank as depicted in fig8 the arm 52 is attached to the base 54 with threaded fasteners 55 providing the mounting means this latter arrangement provides adjustment and flexibility of using the tanks on different makes and models of motorcycles the other end of the undercarriage arm 52 is attached directly to the motorcycle chassis this attachment is normally made by removing the fastening hardware from the rear shock absorbers and the rear fender and interpositioning the arm 52 this provides a rigid mount with sufficient structural integrity to support the tank in a cantilever fashion the shape of this arm 52 may be flat as depicted in fig3 and 5 or.