I read where you were messing around with the white wire. This wire is for a headlight and hooking it up anywhere else can cause the magneto to be shorted out. Until you get a headlight meant for one of these cover the end of the white wire with tape so it does not ground out your magneto.
The fuel mix screw you lost also had a spring that was to keep the screw from backing out. If you replace the screw without a spring you will lose your new part real fast. If they do not send you a spring one from a ball point pen will work with minor modification, usually just shortening it up.
That it ran for a few seconds is encouraging. At least you know it will run, eventually