Burnt Wire
You need to figure this out. If you unhook the yellow start wire at the start
relay what happens. Does the discharge go away? I doubt the ammeter is "bad" in that sense
Bear in mind THERE HAS BEEN CASES where the igntion switch itself was bad---the contacts inside the switch started to "float around" inside and make odd, unwanted connection. Maybe your start circuit is contacting the metal case of the switch
HOW WOULD YOU confirm?
One way is to disconnect the ignition switch. clip a continuity device to the yellow start wire and ground. Twist key to start and check for short to ground. Then do the same with battery lead to switch and then other sitch leads. Again, do all ths with swtich disconnected
If that does not show up anything. disconnect the yellow start wire at the start relay. With the ignition switch connector also disconnected, check the yellow start wire to ground it should be OPEN
Now do same with brown "bypass" IGN2 wire. Unhook coil + wire. Unhook wires from ballast resistor. Check brown wire for short to ground.