Check you have the insulating washers in correct place on points bolt. You probably have a green wire plugged into a red/green somewhere or another earth/ground lead in wrong place. It sounds like it's going through some sort of load or fuse would blow instantly. 10 amp will work as long as you don't have any lights on. If you have an old indicator/bulb holder (21w~23w bulb) connect it across fuse contacts. (leaver fuse out, alligator/crocodile clips on leads) If you have a short, the bulb will light up. Leave it there while you check various connections.It saves on blowing a ton of fuses while troubleshooting. The light green/red neutral wire is a grounding wire, it normally will have battery voltage after neutral light bulb (bulb is load so fuse doesn't blow) If you have bulb holders in speedo and tach, neutral will have black in and red/green out